Merge pull request #4 from eugenp/master

Updating local repository

.gitignore

@@ -85,5 +85,6 @@ transaction.log
 *-shell.log
 
 apache-cxf/cxf-aegis/baeldung.xml
+testing-modules/report-*.json
 
 libraries-2/*.db

algorithms-miscellaneous-6/README.md

@@ -8,4 +8,5 @@
 - [Introduction to Greedy Algorithms with Java](https://www.baeldung.com/java-greedy-algorithms)
 - [The Caesar Cipher in Java](https://www.baeldung.com/java-caesar-cipher)
 - [Implementing a 2048 Solver in Java](https://www.baeldung.com/2048-java-solver)
+- [Finding Top K Elements in an Array](https://www.baeldung.com/java-array-top-elements)
 - More articles: [[<-- prev]](/../algorithms-miscellaneous-5)

algorithms-searching/src/main/java/com/baeldung/algorithms/kthsmallest/KthSmallest.java

@@ -0,0 +1,126 @@
+package com.baeldung.algorithms.kthsmallest;
+
+import java.util.Arrays;
+import java.util.NoSuchElementException;
+
+import static java.lang.Math.max;
+import static java.lang.Math.min;
+
+public class KthSmallest {
+
+    public static int findKthSmallestElement(int k, int[] list1, int[] list2)  throws NoSuchElementException, IllegalArgumentException {
+
+        checkInput(k, list1, list2);
+
+        // we are looking for the minimum value
+        if(k == 1) {
+            return min(list1[0], list2[0]);
+        }
+
+        // we are looking for the maximum value
+        if(list1.length + list2.length == k) {
+            return max(list1[list1.length-1], list2[list2.length-1]);
+        }
+
+        // swap lists if needed to make sure we take at least one element from list1
+        if(k <= list2.length && list2[k-1] < list1[0]) {
+            int[] list1_ = list1;
+            list1 = list2;
+            list2 = list1_;
+        }
+
+        // correct left boundary if k is bigger than the size of list2
+        int left = k < list2.length ? 0 : k - list2.length - 1;
+
+        // the inital right boundary cannot exceed the list1
+        int right = min(k-1, list1.length - 1);
+
+        int nElementsList1, nElementsList2;
+
+        // binary search
+        do {
+            nElementsList1 = ((left + right) / 2) + 1;
+            nElementsList2 = k - nElementsList1;
+
+            if(nElementsList2 > 0) {
+                if (list1[nElementsList1 - 1] > list2[nElementsList2 - 1]) {
+                    right = nElementsList1 - 2;
+                } else {
+                    left = nElementsList1;
+                }
+            }
+        } while(!kthSmallesElementFound(list1, list2, nElementsList1, nElementsList2));
+
+        return nElementsList2 == 0 ? list1[nElementsList1-1] : max(list1[nElementsList1-1], list2[nElementsList2-1]);
+    }
+
+    private static boolean kthSmallesElementFound(int[] list1, int[] list2, int nElementsList1, int nElementsList2) {
+
+        // we do not take any element from the second list
+        if(nElementsList2 < 1) {
+            return true;
+        }
+
+        if(list1[nElementsList1-1] == list2[nElementsList2-1]) {
+            return true;
+        }
+
+        if(nElementsList1 == list1.length) {
+            return list1[nElementsList1-1] <= list2[nElementsList2];
+        }
+
+        if(nElementsList2 == list2.length) {
+            return list2[nElementsList2-1] <= list1[nElementsList1];
+        }
+
+        return list1[nElementsList1-1] <= list2[nElementsList2] && list2[nElementsList2-1] <= list1[nElementsList1];
+    }
+
+
+    private static void checkInput(int k, int[] list1, int[] list2) throws NoSuchElementException, IllegalArgumentException {
+
+        if(list1 == null || list2 == null || k < 1) {
+            throw new IllegalArgumentException();
+        }
+
+        if(list1.length == 0 || list2.length == 0) {
+            throw new IllegalArgumentException();
+        }
+
+        if(k > list1.length + list2.length) {
+            throw new NoSuchElementException();
+        }
+    }
+
+    public static int getKthElementSorted(int[] list1, int[] list2, int k) {
+
+        int length1 = list1.length, length2 = list2.length;
+        int[] combinedArray = new int[length1 + length2];
+        System.arraycopy(list1, 0, combinedArray, 0, list1.length);
+        System.arraycopy(list2, 0, combinedArray, list1.length, list2.length);
+        Arrays.sort(combinedArray);
+
+        return combinedArray[k-1];
+    }
+
+    public static int getKthElementMerge(int[] list1, int[] list2, int k) {
+
+        int i1 = 0, i2 = 0;
+
+        while(i1 < list1.length && i2 < list2.length && (i1 + i2) < k) {
+            if(list1[i1] < list2[i2]) {
+                i1++;
+            } else {
+                i2++;
+            }
+        }
+
+        if((i1 + i2) < k) {
+            return i1 < list1.length ? list1[k - i2 - 1] : list2[k - i1 - 1];
+        } else if(i1 > 0 && i2 > 0) {
+            return Math.max(list1[i1-1], list2[i2-1]);
+        } else {
+            return i1 == 0 ? list2[i2-1] : list1[i1-1];
+        }
+    }
+}

algorithms-searching/src/test/java/com/baeldung/algorithms/kthsmallest/KthSmallestUnitTest.java

@@ -0,0 +1,288 @@
+package com.baeldung.algorithms.kthsmallest;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.function.Executable;
+
+import java.util.*;
+
+import static com.baeldung.algorithms.kthsmallest.KthSmallest.*;
+import static org.junit.jupiter.api.Assertions.*;
+
+public class KthSmallestUnitTest {
+
+    @Nested
+    class Exceptions {
+
+        @Test
+        public void when_at_least_one_list_is_null_then_an_exception_is_thrown() {
+
+            Executable executable1 = () -> findKthSmallestElement(1, null, null);
+            Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, null);
+            Executable executable3 = () -> findKthSmallestElement(1, null, new int[]{2});
+
+            assertThrows(IllegalArgumentException.class, executable1);
+            assertThrows(IllegalArgumentException.class, executable2);
+            assertThrows(IllegalArgumentException.class, executable3);
+        }
+
+        @Test
+        public void when_at_least_one_list_is_empty_then_an_exception_is_thrown() {
+
+            Executable executable1 = () -> findKthSmallestElement(1, new int[]{}, new int[]{2});
+            Executable executable2 = () -> findKthSmallestElement(1, new int[]{2}, new int[]{});
+            Executable executable3 = () -> findKthSmallestElement(1, new int[]{}, new int[]{});
+
+            assertThrows(IllegalArgumentException.class, executable1);
+            assertThrows(IllegalArgumentException.class, executable2);
+            assertThrows(IllegalArgumentException.class, executable3);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_0_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(-1, new int[]{2}, new int[]{2});
+            assertThrows(IllegalArgumentException.class, executable1);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_1_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(0, new int[]{2}, new int[]{2});
+            assertThrows(IllegalArgumentException.class, executable1);
+        }
+
+        @Test
+        public void when_k_bigger_then_the_two_lists_then_an_exception_is_thrown() {
+            Executable executable1 = () -> findKthSmallestElement(6, new int[]{1, 5, 6}, new int[]{2, 5});
+            assertThrows(NoSuchElementException.class, executable1);
+        }
+
+    }
+
+    @Nested
+    class K_is_smaller_than_the_size_of_list1_and_the_size_of_list2 {
+
+        @Test
+        public void when_k_is_1_then_the_smallest_element_is_returned_from_list1() {
+            int result = findKthSmallestElement(1, new int[]{2, 7}, new int[]{3, 5});
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void when_k_is_1_then_the_smallest_element_is_returned_list2() {
+            int result = findKthSmallestElement(1, new int[]{3, 5}, new int[]{2, 7});
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void when_kth_element_is_smallest_element_and_occurs_in_both_lists() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(1, list1, list2);
+            assertEquals(1, result);
+        }
+
+        @Test
+        public void when_kth_element_is_smallest_element_and_occurs_in_both_lists2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(2, list1, list2);
+            assertEquals(1, result);
+        }
+
+        @Test
+        public void when_kth_element_is_largest_element_and_occurs_in_both_lists_1() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_kth_element_is_largest_element_and_occurs_in_both_lists_2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_kth_element_and_occurs_in_both_lists() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{0, 2, 3};
+            int result = findKthSmallestElement(3, list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_kth_element_is_in_first_list() {
+            int[] list1 = new int[]{1,2,3,4};
+            int[] list2 = new int[]{1,3,4,5};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_kth_is_in_second_list() {
+            int[] list1 = new int[]{1,3,4,4};
+            int[] list2 = new int[]{1,2,4,5};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(2, result);
+        }
+
+        @Test
+        public void and_elements_in_first_list_are_all_smaller_than_second_list() {
+            int[] list1 = new int[]{1,3,7,9};
+            int[] list2 = new int[]{11,12,14,15};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(7, result);
+        }
+
+        @Test
+        public void and_elements_in_first_list_are_all_smaller_than_second_list2() {
+            int[] list1 = new int[]{1,3,7,9};
+            int[] list2 = new int[]{11,12,14,15};
+            int result = findKthSmallestElement(4,  list1, list2);
+            assertEquals(9, result);
+        }
+
+        @Test
+        public void and_only_elements_from_second_list_are_part_of_result() {
+            int[] list1 = new int[]{11,12,14,15};
+            int[] list2 = new int[]{1,3,7,9};
+            int result = findKthSmallestElement(3,  list1, list2);
+            assertEquals(7, result);
+        }
+
+        @Test
+        public void and_only_elements_from_second_list_are_part_of_result2() {
+            int[] list1 = new int[]{11,12,14,15};
+            int[] list2 = new int[]{1,3,7,9};
+            int result = findKthSmallestElement(4,  list1, list2);
+            assertEquals(9, result);
+        }
+    }
+
+    @Nested
+    class K_is_bigger_than_the_size_of_at_least_one_of_the_lists {
+
+        @Test
+        public void k_is_smaller_than_list1_and_bigger_than_list2() {
+            int[] list1 = new int[]{1, 2, 3, 4, 7, 9};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void k_is_bigger_than_list1_and_smaller_than_list2() {
+            int[] list1 = new int[]{1, 2, 3};
+            int[] list2 = new int[]{1, 2, 3, 4, 7, 9};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_smaller_than_first_list() {
+            int[] list1 = new int[]{9, 11, 13, 55};
+            int[] list2 = new int[]{1, 2, 3, 7};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(11, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_elements_in_second_list_are_all_bigger_than_first_list() {
+            int[] list1 = new int[]{1, 2, 3, 7};
+            int[] list2 = new int[]{9, 11, 13, 55};
+            int result = findKthSmallestElement(6, list1, list2);
+            assertEquals(11, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists() {
+            int[] list1 = new int[]{3, 7, 9, 11, 55};
+            int[] list2 = new int[]{1, 2, 3, 7, 13};
+            int result = findKthSmallestElement(7, list1, list2);
+            assertEquals(9, result);
+        }
+
+        @Test
+        public void when_k_is_bigger_than_the_size_of_both_lists_and_list1_has_more_elements_than_list2() {
+            int[] list1 = new int[]{3, 7, 9, 11, 55, 77, 100, 200};
+            int[] list2 = new int[]{1, 2, 3, 7, 13};
+            int result = findKthSmallestElement(11, list1, list2);
+            assertEquals(77, result);
+        }
+
+        @Test
+        public void max_test() {
+            int[] list1 = new int[]{100, 200};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(4, list1, list2);
+            assertEquals(100, result);
+        }
+
+        @Test
+        public void max_test2() {
+            int[] list1 = new int[]{100, 200};
+            int[] list2 = new int[]{1, 2, 3};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(200, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_in_list2() {
+            int[] list1 = new int[]{1, 2, 5};
+            int[] list2 = new int[]{1, 3, 4, 7};
+            int result = findKthSmallestElement(4, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list2() {
+            int[] list1 = new int[]{1, 2, 5};
+            int[] list2 = new int[]{3, 4, 7};
+            int result = findKthSmallestElement(3, list1, list2);
+            assertEquals(3, result);
+        }
+
+        @Test
+        public void when_k_is_smaller_than_the_size_of_both_lists_and_kth_element_is_smallest_in_list23() {
+            int[] list1 = new int[]{3, 11, 27, 53, 90};
+            int[] list2 = new int[]{4, 20, 21, 100};
+            int result = findKthSmallestElement(5, list1, list2);
+            assertEquals(21, result);
+        }
+    }
+
+//    @Test
+//    public void randomTests() {
+//        IntStream.range(1, 100000).forEach(i -> random());
+//    }
+
+    private void random() {
+
+        Random random = new Random();
+        int length1 = (Math.abs(random.nextInt())) % 1000 + 1;
+        int length2 = (Math.abs(random.nextInt())) % 1000 + 1;
+
+        int[] list1 = sortedRandomIntArrayOfLength(length1);
+        int[] list2 = sortedRandomIntArrayOfLength(length2);
+
+        int k = (Math.abs(random.nextInt()) % (length1 + length2)) + 1 ;
+
+        int result = findKthSmallestElement(k,  list1, list2);
+
+        int result2 = getKthElementSorted(list1, list2, k);
+
+        int result3 = getKthElementMerge(list1, list2, k);
+
+        assertEquals(result2, result);
+        assertEquals(result2, result3);
+    }
+
+    private int[] sortedRandomIntArrayOfLength(int length) {
+        int[] intArray = new Random().ints(length).toArray();
+        Arrays.sort(intArray);
+        return intArray;
+    }
+}

apache-cxf/README.md

@@ -7,4 +7,3 @@ This module contains articles about Apache CXF
 - [Apache CXF Support for RESTful Web Services](https://www.baeldung.com/apache-cxf-rest-api)
 - [A Guide to Apache CXF with Spring](https://www.baeldung.com/apache-cxf-with-spring)
 - [Introduction to Apache CXF](https://www.baeldung.com/introduction-to-apache-cxf)
-- [Server-Sent Events (SSE) In JAX-RS](https://www.baeldung.com/java-ee-jax-rs-sse)

apache-cxf/sse-jaxrs/README.md

@@ -0,0 +1,3 @@
+### Relevant Articles:
+
+- [Server-Sent Events (SSE) In JAX-RS](https://www.baeldung.com/java-ee-jax-rs-sse)

apache-poi/src/main/java/com/baeldung/poi/excel/setformula/ExcelFormula.java

@@ -0,0 +1,26 @@
+package com.baeldung.poi.excel.setformula;
+
+import org.apache.poi.xssf.usermodel.XSSFCell;
+import org.apache.poi.xssf.usermodel.XSSFFormulaEvaluator;
+import org.apache.poi.xssf.usermodel.XSSFSheet;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+
+public class ExcelFormula {
+    public double setFormula(String fileLocation, XSSFWorkbook wb, String formula) throws IOException {
+        XSSFSheet sheet = wb.getSheetAt(0);
+        int lastCellNum = sheet.getRow(0).getLastCellNum();
+        XSSFCell formulaCell = sheet.getRow(0).createCell(lastCellNum);
+        formulaCell.setCellFormula(formula);
+        XSSFFormulaEvaluator formulaEvaluator = wb.getCreationHelper().createFormulaEvaluator();
+        formulaEvaluator.evaluateFormulaCell(formulaCell);
+        FileOutputStream fileOut = new FileOutputStream(new File(fileLocation));
+        wb.write(fileOut);
+        wb.close();
+        fileOut.close();
+        return formulaCell.getNumericCellValue();
+    }
+}

apache-poi/src/test/java/com/baeldung/poi/excel/setformula/ExcelFormulaUnitTest.java

@@ -0,0 +1,51 @@
+package com.baeldung.poi.excel.setformula;
+
+import org.apache.poi.ss.util.CellReference;
+import org.apache.poi.xssf.usermodel.XSSFSheet;
+import org.apache.poi.xssf.usermodel.XSSFWorkbook;
+import org.junit.Assert;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+import java.net.URISyntaxException;
+import java.nio.file.Paths;
+
+class ExcelFormulaUnitTest {
+    private static String FILE_NAME = "com/baeldung/poi/excel/setformula/SetFormulaTest.xlsx";
+    private String fileLocation;
+    private ExcelFormula excelFormula;
+
+    @BeforeEach
+    public void setup() throws URISyntaxException {
+        fileLocation = Paths.get(ClassLoader.getSystemResource(FILE_NAME).toURI()).toString();
+        excelFormula = new ExcelFormula();
+    }
+
+    @Test
+    void givenExcelData_whenSetFormula_thenSuccess() throws IOException {
+        FileInputStream inputStream = new FileInputStream(new File(fileLocation));
+        XSSFWorkbook wb = new XSSFWorkbook(inputStream);
+        XSSFSheet sheet = wb.getSheetAt(0);
+        double resultColumnA = 0;
+        double resultColumnB = 0;
+        for (int row = 0; row <= sheet.getLastRowNum(); row++) {
+            resultColumnA += sheet.getRow(row).getCell(0).getNumericCellValue();
+            resultColumnB += sheet.getRow(row).getCell(1).getNumericCellValue();
+        }
+        String colNameA = CellReference.convertNumToColString(0);
+        String colNameB = CellReference.convertNumToColString(1);
+        String startCellA = colNameA + 1;
+        String stopCellA = colNameA + (sheet.getLastRowNum() + 1);
+        String sumFormulaForColumnA = String.format("SUM(%s:%s)", startCellA, stopCellA);
+        String startCellB = colNameB + 1;
+        String stopCellB = colNameB + (sheet.getLastRowNum() + 1);
+        String sumFormulaForColumnB = String.format("SUM(%s:%s)", startCellB, stopCellB);
+
+        double resultValue = excelFormula.setFormula(fileLocation, wb, sumFormulaForColumnA + "-" + sumFormulaForColumnB);
+
+        Assert.assertEquals(resultColumnA - resultColumnB, resultValue, 0d);
+    }
+}

apache-shiro/README.md

@@ -6,4 +6,4 @@ This module contains articles about Apache Shiro
 
 - [Introduction to Apache Shiro](https://www.baeldung.com/apache-shiro)
 - [Permissions-Based Access Control with Apache Shiro](https://www.baeldung.com/apache-shiro-access-control)
-
+- [Spring Security vs Apache Shiro](https://www.baeldung.com/spring-security-vs-apache-shiro)

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseDateTimeFormatterUnitTest.java

@@ -31,6 +31,6 @@ public class UseDateTimeFormatterUnitTest {
     public void givenALocalDate_whenFormattingWithStyleAndLocale_thenPass() {
         String result = subject.formatWithStyleAndLocale(localDateTime, FormatStyle.MEDIUM, Locale.UK);
 
-        assertThat(result).isEqualTo("25 Jan 2015, 06:30:00");
+        assertThat(result).isEqualTo("25-Jan-2015 06:30:00");
     }
 }

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseToInstantUnitTest.java

@@ -3,6 +3,7 @@ package com.baeldung.datetime;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.time.LocalDateTime;
+import java.time.ZoneId;
 import java.util.Calendar;
 import java.util.Date;
 import java.util.GregorianCalendar;
@@ -24,10 +25,11 @@ public class UseToInstantUnitTest {
 
     @Test
     public void givenADate_whenConvertingToLocalDate_thenAsExpected() {
-        Date givenDate = new Date(1465817690000L);
+        LocalDateTime currentDateTime = LocalDateTime.now();
+        Date givenDate = Date.from(currentDateTime.atZone(ZoneId.systemDefault()).toInstant());
 
         LocalDateTime localDateTime = subject.convertDateToLocalDate(givenDate);
 
-        assertThat(localDateTime).isEqualTo("2016-06-13T13:34:50");
+        assertThat(localDateTime).isEqualTo(currentDateTime);
     }
 }

core-java-modules/core-java-8-datetime/src/test/java/com/baeldung/datetime/UseZonedDateTimeUnitTest.java

@@ -54,7 +54,7 @@ public class UseZonedDateTimeUnitTest {
     @Test
     public void givenAStringWithTimeZone_whenParsing_thenEqualsExpected() {
         ZonedDateTime resultFromString = zonedDateTime.getZonedDateTimeUsingParseMethod("2015-05-03T10:15:30+01:00[Europe/Paris]");
-        ZonedDateTime resultFromLocalDateTime = ZonedDateTime.of(2015, 5, 3, 11, 15, 30, 0, ZoneId.of("Europe/Paris"));
+        ZonedDateTime resultFromLocalDateTime = ZonedDateTime.of(2015, 5, 3, 10, 15, 30, 0, ZoneId.of("Europe/Paris"));
 
         assertThat(resultFromString.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));
         assertThat(resultFromLocalDateTime.getZone()).isEqualTo(ZoneId.of("Europe/Paris"));

core-java-modules/core-java-9-new-features/README.md

@@ -14,3 +14,4 @@ This module contains articles about core Java features that have been introduced
 - [Java 9 Reactive Streams](https://www.baeldung.com/java-9-reactive-streams)
 - [Multi-Release JAR Files with Maven](https://www.baeldung.com/maven-multi-release-jars)
 - [The Difference between RxJava API and the Java 9 Flow API](https://www.baeldung.com/rxjava-vs-java-flow-api)
+- [How to Get a Name of a Method Being Executed?](https://www.baeldung.com/java-name-of-executing-method)

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/arraycompare/Plane.java

@@ -0,0 +1,39 @@
+package com.baeldung.arraycompare;
+
+import java.util.Objects;
+
+public class Plane {
+
+    private final String name;
+
+    private final String model;
+
+    public Plane(String name, String model) {
+
+        this.name = name;
+        this.model = model;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public String getModel() {
+        return model;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o)
+            return true;
+        if (o == null || getClass() != o.getClass())
+            return false;
+        Plane plane = (Plane) o;
+        return Objects.equals(name, plane.name) && Objects.equals(model, plane.model);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(name, model);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/DeepEqualsCompareUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class DeepEqualsCompareUnitTest {
+
+    @Test
+    public void givenSameContents_whenDeepEquals_thenTrue() {
+        final Plane[][] planes1 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isTrue();
+    }
+
+    @Test
+    public void givenSameContentsWithDifferentOrder_whenDeepEquals_thenFalse() {
+        final Plane[][] planes1 = new Plane[][] { new Plane[] { new Plane("Plane 1", "A320") },
+            new Plane[] { new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] { new Plane[] { new Plane("Plane 2", "B738") },
+            new Plane[] { new Plane("Plane 1", "A320") } };
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isFalse();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/EqualsCompareUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class EqualsCompareUnitTest {
+
+    @Test
+    public void givenSameContents_whenEquals_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(Arrays.equals(planes1, planes2)).isTrue();
+    }
+
+    @Test
+    public void givenSameContentsDifferentOrder_whenEquals_thenFalse() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "B738", "A320", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(Arrays.equals(planes1, planes2)).isFalse();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/LengthsCompareUnitTest.java

@@ -0,0 +1,18 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class LengthsCompareUnitTest {
+
+    @Test
+    public void givenSameContent_whenSizeCompare_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final Integer[] quantities = new Integer[] { 10, 12, 34, 45, 12, 43, 5, 2 };
+
+        assertThat(planes1).hasSize(8);
+        assertThat(quantities).hasSize(8);
+    }
+}
+

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/OrderCompareUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertTrue;
+
+public class OrderCompareUnitTest {
+    @Test
+    public void givenSameContentDifferentOrder_whenSortedAndDeepEquals_thenTrue() {
+        final Plane[][] planes1 = new Plane[][] {
+            new Plane[] { new Plane("Plane 1", "A320"), new Plane("Plane 2", "B738") } };
+        final Plane[][] planes2 = new Plane[][] {
+            new Plane[] { new Plane("Plane 2", "B738"), new Plane("Plane 1", "A320") } };
+
+        Comparator<Plane> planeComparator = (o1, o2) -> {
+            if (o1.getName()
+                .equals(o2.getName())) {
+                return o2.getModel()
+                    .compareTo(o1.getModel());
+            }
+            return o2.getName()
+                .compareTo(o1.getName());
+        };
+        Arrays.sort(planes1[0], planeComparator);
+        Arrays.sort(planes2[0], planeComparator);
+
+        assertThat(Arrays.deepEquals(planes1, planes2)).isTrue();
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycompare/ReferenceCompareUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.arraycompare;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class ReferenceCompareUnitTest {
+
+    @Test
+    public void givenSameReferences_whenSame_thenTrue() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = planes1;
+
+        assertThat(planes1).isSameAs(planes2);
+
+        planes2[0] = "747";
+
+        assertThat(planes1).isSameAs(planes2);
+        assertThat(planes2[0]).isEqualTo("747");
+        assertThat(planes1[0]).isEqualTo("747");
+    }
+
+    @Test
+    public void givenSameContentDifferentReferences_whenSame_thenFalse() {
+        final String[] planes1 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+        final String[] planes2 = new String[] { "A320", "B738", "A321", "A319", "B77W", "B737", "A333", "A332" };
+
+        assertThat(planes1).isNotSameAs(planes2);
+    }
+}

core-java-modules/core-java-collections-2/src/test/java/com/baeldung/collections/sorting/JavaSortingUnitTest.java

@@ -5,7 +5,16 @@ import org.apache.commons.lang3.ArrayUtils;
 import org.junit.Before;
 import org.junit.Test;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.LinkedHashMap;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Map;
 import java.util.Map.Entry;
 
 import static org.junit.Assert.assertTrue;
@@ -138,7 +147,7 @@ public class JavaSortingUnitTest {
         HashSet<Integer> descSortedIntegersSet = new LinkedHashSet<>(Arrays.asList(255, 200, 123, 89, 88, 66, 7, 5, 1));
 
         ArrayList<Integer> list = new ArrayList<>(integersSet);
-        list.sort((i1, i2) -> i2 - i1);
+        list.sort(Comparator.reverseOrder());
         integersSet = new LinkedHashSet<>(list);
 
         assertTrue(Arrays.equals(integersSet.toArray(), descSortedIntegersSet.toArray()));

core-java-modules/core-java-collections-3/README.md

@@ -3,6 +3,7 @@
 ## Core Java Collections Cookbooks and Examples
 
 ### Relevant Articles: 
+
 - [Time Comparison of Arrays.sort(Object[]) and Arrays.sort(int[])](https://www.baeldung.com/arrays-sortobject-vs-sortint)
 - [Java ArrayList vs Vector](https://www.baeldung.com/java-arraylist-vs-vector)
 - [Differences Between HashMap and Hashtable](https://www.baeldung.com/hashmap-hashtable-differences)
@@ -10,3 +11,4 @@
 - [Performance of contains() in a HashSet vs ArrayList](https://www.baeldung.com/java-hashset-arraylist-contains-performance)
 - [Fail-Safe Iterator vs Fail-Fast Iterator](https://www.baeldung.com/java-fail-safe-vs-fail-fast-iterator)
 - [Quick Guide to the Java Stack](https://www.baeldung.com/java-stack)
+- [Convert an Array of Primitives to a List](https://www.baeldung.com/java-primitive-array-to-list)

core-java-modules/core-java-collections-3/pom.xml

@@ -16,6 +16,11 @@
     </parent>
 
     <dependencies>
+        <dependency>
+            <groupId>org.openjdk.jol</groupId>
+            <artifactId>jol-core</artifactId>
+            <version>${jol-core.version}</version>
+        </dependency>
         <dependency>
             <groupId>org.openjdk.jmh</groupId>
             <artifactId>jmh-core</artifactId>
@@ -37,6 +42,7 @@
     <properties>
         <openjdk.jmh.version>1.19</openjdk.jmh.version>
         <assertj.version>3.11.1</assertj.version>
+        <jol-core.version>0.10</jol-core.version>
     </properties>
 
 </project>

core-java-modules/core-java-collections-3/src/test/java/com/baeldung/collections/bitset/BitSetUnitTest.java

@@ -0,0 +1,178 @@
+package com.baeldung.collections.bitset;
+
+import org.junit.Test;
+import org.openjdk.jol.info.ClassLayout;
+import org.openjdk.jol.info.GraphLayout;
+
+import java.util.BitSet;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class BitSetUnitTest {
+
+    @Test
+    public void givenBoolArray_whenMemoryLayout_thenConsumeMoreThanOneBit() {
+        boolean[] bits = new boolean[1024 * 1024];
+
+        System.out.println(ClassLayout.parseInstance(bits).toPrintable());
+    }
+
+    @Test
+    public void givenBitSet_whenMemoryLayout_thenConsumeOneBitPerFlag() {
+        BitSet bitSet = new BitSet(1024 * 1024);
+
+        System.out.println(GraphLayout.parseInstance(bitSet).toPrintable());
+    }
+
+    @Test
+    public void givenBitSet_whenSetting_thenShouldBeTrue() {
+        BitSet bitSet = new BitSet();
+
+        bitSet.set(10);
+        assertThat(bitSet.get(10)).isTrue();
+
+        bitSet.set(20, 30);
+        for (int i = 20; i <= 29; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+        assertThat(bitSet.get(30)).isFalse();
+
+        bitSet.set(10, false);
+        assertThat(bitSet.get(10)).isFalse();
+
+        bitSet.set(20, 30, false);
+        for (int i = 20; i <= 30; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenClearing_thenShouldBeFalse() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+        assertThat(bitSet.get(42)).isTrue();
+
+        bitSet.clear(42);
+        assertThat(bitSet.get(42)).isFalse();
+
+        bitSet.set(10, 20);
+        for (int i = 10; i < 20; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+
+        bitSet.clear(10, 20);
+        for (int i = 10; i < 20; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+
+        bitSet.set(10, 20);
+        bitSet.clear();
+        for (int i = 0; i < 100; i++) {
+            assertThat(bitSet.get(i)).isFalse();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenGettingElements_thenShouldReturnRequestedBits() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+
+        assertThat(bitSet.get(42)).isTrue();
+        assertThat(bitSet.get(43)).isFalse();
+
+        bitSet.set(10, 20);
+        BitSet newBitSet = bitSet.get(10, 20);
+        for (int i = 0; i < 10; i++) {
+            assertThat(newBitSet.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenFlip_thenTogglesTrueToFalseAndViceVersa() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(42);
+        bitSet.flip(42);
+        assertThat(bitSet.get(42)).isFalse();
+
+        bitSet.flip(12);
+        assertThat(bitSet.get(12)).isTrue();
+
+        bitSet.flip(30, 40);
+        for (int i = 30; i < 40; i++) {
+            assertThat(bitSet.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenGettingTheSize_thenReturnsTheSize() {
+        BitSet defaultBitSet = new BitSet();
+        assertThat(defaultBitSet.size()).isEqualTo(64);
+
+        BitSet bitSet = new BitSet(1024);
+        assertThat(bitSet.size()).isEqualTo(1024);
+
+        assertThat(bitSet.cardinality()).isEqualTo(0);
+        bitSet.set(10, 30);
+        assertThat(bitSet.cardinality()).isEqualTo(30 - 10);
+
+        assertThat(bitSet.length()).isEqualTo(30);
+        bitSet.set(100);
+        assertThat(bitSet.length()).isEqualTo(101);
+
+        assertThat(bitSet.isEmpty()).isFalse();
+        bitSet.clear();
+        assertThat(bitSet.isEmpty()).isTrue();
+    }
+
+    @Test
+    public void givenBitSet_whenSetOperations_thenShouldReturnAnotherBitSet() {
+        BitSet first = new BitSet();
+        first.set(5, 10);
+
+        BitSet second = new BitSet();
+        second.set(7, 15);
+
+        assertThat(first.intersects(second)).isTrue();
+
+        first.and(second);
+        assertThat(first.get(7)).isTrue();
+        assertThat(first.get(8)).isTrue();
+        assertThat(first.get(9)).isTrue();
+        assertThat(first.get(10)).isFalse();
+
+        first.clear();
+        first.set(5, 10);
+
+        first.xor(second);
+        for (int i = 5; i < 7; i++) {
+            assertThat(first.get(i)).isTrue();
+        }
+        for (int i = 10; i < 15; i++) {
+            assertThat(first.get(i)).isTrue();
+        }
+    }
+
+    @Test
+    public void givenBitSet_whenStream_thenStreamsAllSetBits() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(15, 25);
+
+        bitSet.stream().forEach(System.out::println);
+        assertThat(bitSet.stream().count()).isEqualTo(10);
+    }
+
+    @Test
+    public void givenBitSet_whenNextOrPrev_thenReturnsTheNextOrPrevClearOrSetBit() {
+        BitSet bitSet = new BitSet();
+        bitSet.set(15, 25);
+
+        assertThat(bitSet.nextSetBit(13)).isEqualTo(15);
+        assertThat(bitSet.nextSetBit(25)).isEqualTo(-1);
+
+        assertThat(bitSet.nextClearBit(23)).isEqualTo(25);
+
+        assertThat(bitSet.previousClearBit(24)).isEqualTo(14);
+        assertThat(bitSet.previousSetBit(29)).isEqualTo(24);
+        assertThat(bitSet.previousSetBit(14)).isEqualTo(-1);
+    }
+}

core-java-modules/core-java-collections-list-3/pom.xml

@@ -21,6 +21,12 @@
             <artifactId>commons-collections4</artifactId>
             <version>${commons-collections4.version}</version>
         </dependency>
+        <dependency>
+            <groupId>com.google.guava</groupId>
+            <artifactId>guava</artifactId>
+            <version>${guava.version}</version>
+            <scope>compile</scope>
+        </dependency>
         <dependency>
             <groupId>org.assertj</groupId>
             <artifactId>assertj-core</artifactId>

core-java-modules/core-java-collections-list-3/src/test/java/com/baeldung/list/difference/FindDifferencesBetweenListsUnitTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.list.difference;
+
+import com.google.common.collect.Sets;
+import org.apache.commons.collections4.CollectionUtils;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.stream.Collectors;
+
+import static org.junit.jupiter.api.Assertions.*;
+import static org.assertj.core.api.Assertions.*;
+
+public class FindDifferencesBetweenListsUnitTest {
+
+    private static final List<String> listOne = Arrays.asList("Jack", "Tom", "Sam", "John", "James", "Jack");
+    private static final List<String> listTwo = Arrays.asList("Jack", "Daniel", "Sam", "Alan", "James", "George");
+
+    @Test
+    public void givenLists_whenUsingPlainJavaImpl_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(listOne);
+        differences.removeAll(listTwo);
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingPlainJavaImpl_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(listTwo);
+        differences.removeAll(listOne);
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingJavaStreams_thenDifferencesAreFound() {
+        List<String> differences = listOne.stream()
+                .filter(element -> !listTwo.contains(element))
+                .collect(Collectors.toList());
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingJavaStreams_thenDifferencesAreFound() {
+        List<String> differences = listTwo.stream()
+                .filter(element -> !listOne.contains(element))
+                .collect(Collectors.toList());
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingGoogleGuava_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(Sets.difference(Sets.newHashSet(listOne), Sets.newHashSet(listTwo)));
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactlyInAnyOrder("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingGoogleGuava_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>(Sets.difference(Sets.newHashSet(listTwo), Sets.newHashSet(listOne)));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactlyInAnyOrder("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingApacheCommons_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>((CollectionUtils.removeAll(listOne, listTwo)));
+        assertEquals(2, differences.size());
+        assertThat(differences).containsExactly("Tom", "John");
+    }
+
+    @Test
+    public void givenReverseLists_whenUsingApacheCommons_thenDifferencesAreFound() {
+        List<String> differences = new ArrayList<>((CollectionUtils.removeAll(listTwo, listOne)));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Daniel", "Alan", "George");
+    }
+
+    @Test
+    public void givenLists_whenUsingPlainJavaImpl_thenDifferencesWithDuplicatesAreFound() {
+        List<String> differences = new ArrayList<>(listOne);
+        listTwo.forEach(differences::remove);
+        assertThat(differences).containsExactly("Tom", "John", "Jack");
+    }
+
+    @Test
+    public void givenLists_whenUsingApacheCommons_thenDifferencesWithDuplicatesAreFound() {
+        List<String> differences = new ArrayList<>(CollectionUtils.subtract(listOne, listTwo));
+        assertEquals(3, differences.size());
+        assertThat(differences).containsExactly("Tom", "John", "Jack");
+    }
+
+}

core-java-modules/core-java-collections-maps-2/pom.xml

@@ -21,20 +21,15 @@
             <version>${eclipse-collections.version}</version>
         </dependency>
         <dependency>
-            <groupId>net.sf.trove4j</groupId>
+            <groupId>com.carrotsearch</groupId>
-            <artifactId>trove4j</artifactId>
+            <artifactId>hppc</artifactId>
-            <version>${trove4j.version}</version>
+            <version>${hppc.version}</version>
         </dependency>
         <dependency>
             <groupId>it.unimi.dsi</groupId>
             <artifactId>fastutil</artifactId>
             <version>${fastutil.version}</version>
         </dependency>
-        <dependency>
-            <groupId>colt</groupId>
-            <artifactId>colt</artifactId>
-            <version>${colt.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.commons</groupId>
             <artifactId>commons-lang3</artifactId>
@@ -69,9 +64,8 @@
         <commons-collections4.version>4.1</commons-collections4.version>
         <avaitility.version>1.7.0</avaitility.version>
         <eclipse-collections.version>8.2.0</eclipse-collections.version>
-        <trove4j.version>3.0.2</trove4j.version>
+        <hppc.version>0.7.2</hppc.version>
         <fastutil.version>8.1.0</fastutil.version>
-        <colt.version>1.2.0</colt.version>
         <assertj.version>3.11.1</assertj.version>
     </properties>
 

core-java-modules/core-java-collections-maps-2/src/main/java/com/baeldung/map/primitives/PrimitiveMaps.java

@@ -1,29 +1,68 @@
 package com.baeldung.map.primitives;
 
-import cern.colt.map.AbstractIntDoubleMap;
+import com.carrotsearch.hppc.IntLongHashMap;
-import cern.colt.map.OpenIntDoubleHashMap;
+import com.carrotsearch.hppc.IntLongScatterMap;
-import gnu.trove.map.TDoubleIntMap;
+import com.carrotsearch.hppc.IntObjectHashMap;
-import gnu.trove.map.hash.TDoubleIntHashMap;
+import com.carrotsearch.hppc.IntObjectMap;
+import com.carrotsearch.hppc.IntObjectScatterMap;
+
 import it.unimi.dsi.fastutil.ints.Int2BooleanMap;
+import it.unimi.dsi.fastutil.ints.Int2BooleanMaps;
 import it.unimi.dsi.fastutil.ints.Int2BooleanOpenHashMap;
 import it.unimi.dsi.fastutil.ints.Int2BooleanSortedMap;
 import it.unimi.dsi.fastutil.ints.Int2BooleanSortedMaps;
+import it.unimi.dsi.fastutil.objects.ObjectIterator;
+
 import org.eclipse.collections.api.map.primitive.ImmutableIntIntMap;
 import org.eclipse.collections.api.map.primitive.MutableIntIntMap;
 import org.eclipse.collections.api.map.primitive.MutableObjectDoubleMap;
 import org.eclipse.collections.impl.factory.primitive.IntIntMaps;
 import org.eclipse.collections.impl.factory.primitive.ObjectDoubleMaps;
 
+import static java.lang.String.format;
+
+import java.math.BigDecimal;
+
 public class PrimitiveMaps {
 
     public static void main(String[] args) {
 
+        hppcMap();
         eclipseCollectionsMap();
-        troveMap();
-        coltMap();
         fastutilMap();
     }
 
+    private static void hppcMap() {
+        //Regular maps
+        IntLongHashMap intLongHashMap = new IntLongHashMap();
+        intLongHashMap.put(25,1L);
+        intLongHashMap.put(150,Long.MAX_VALUE);
+        intLongHashMap.put(1,0L);
+        
+        intLongHashMap.get(150);
+
+        IntObjectMap<BigDecimal> intObjectMap = new IntObjectHashMap<BigDecimal>();
+        intObjectMap.put(1, BigDecimal.valueOf(1));
+        intObjectMap.put(2, BigDecimal.valueOf(2500));
+
+        BigDecimal value = intObjectMap.get(2);
+
+        //Scatter maps
+        IntLongScatterMap intLongScatterMap = new IntLongScatterMap();
+        intLongScatterMap.put(1, 1L);
+        intLongScatterMap.put(2, -2L);
+        intLongScatterMap.put(1000,0L);    
+
+        intLongScatterMap.get(1000);
+
+        IntObjectScatterMap<BigDecimal> intObjectScatterMap = new IntObjectScatterMap<BigDecimal>();
+        intObjectScatterMap.put(1, BigDecimal.valueOf(1));
+        intObjectScatterMap.put(2, BigDecimal.valueOf(2500));
+
+        value = intObjectScatterMap.get(2);
+    }
+
+
     private static void fastutilMap() {
         Int2BooleanMap int2BooleanMap = new Int2BooleanOpenHashMap();
         int2BooleanMap.put(1, true);
@@ -32,13 +71,19 @@ public class PrimitiveMaps {
 
         boolean value = int2BooleanMap.get(1);
 
-        Int2BooleanSortedMap int2BooleanSorted = Int2BooleanSortedMaps.EMPTY_MAP;
+        //Lambda style iteration
-    }
+        Int2BooleanMaps.fastForEach(int2BooleanMap, entry -> {
+            System.out.println(String.format("Key: %d, Value: %b",entry.getIntKey(),entry.getBooleanValue()));
+        });
+
+        //Iterator based loop
+        ObjectIterator<Int2BooleanMap.Entry> iterator = Int2BooleanMaps.fastIterator(int2BooleanMap);
+        while(iterator.hasNext()) {
+            Int2BooleanMap.Entry entry = iterator.next();
+            System.out.println(String.format("Key: %d, Value: %b",entry.getIntKey(),entry.getBooleanValue()));
+
+        }
 
-    private static void coltMap() {
-        AbstractIntDoubleMap map = new OpenIntDoubleHashMap();
-        map.put(1, 4.5);
-        double value = map.get(1);
     }
 
     private static void eclipseCollectionsMap() {
@@ -53,17 +98,5 @@ public class PrimitiveMaps {
         dObject.addToValue("stability", 0.8);
     }
 
-    private static void troveMap() {
-        double[] doubles = new double[] {1.2, 4.5, 0.3};
-        int[] ints = new int[] {1, 4, 0};
 
-        TDoubleIntMap doubleIntMap = new TDoubleIntHashMap(doubles, ints);
-
-        doubleIntMap.put(1.2, 22);
-        doubleIntMap.put(4.5, 16);
-
-        doubleIntMap.adjustValue(1.2, 1);
-        doubleIntMap.adjustValue(4.5, 4);
-        doubleIntMap.adjustValue(0.3, 7);
-    }
 }

core-java-modules/core-java-concurrency-advanced-3/src/test/java/com/baeldung/workstealing/PrimeNumbersManualTest.java

@@ -15,7 +15,15 @@ import java.util.logging.Logger;
 
 import static org.junit.Assert.fail;
 
-public class PrimeNumbersUnitManualTest {
+/**
+ * This test expects the file target/test-classes/META-INF/BenchmarkList to be present.
+ *
+ * Before running the test ensure that the file is present. 
+ * If not, please run mvn install on the module.
+ * 
+ */
+
+public class PrimeNumbersManualTest {
 
     private static Logger logger = Logger.getAnonymousLogger();
 

core-java-modules/core-java-concurrency-advanced/src/main/java/com/baeldung/threadlocal/ThreadLocalAwareThreadPool.java

@@ -0,0 +1,25 @@
+package com.baeldung.threadlocal;
+
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.RejectedExecutionHandler;
+import java.util.concurrent.ThreadFactory;
+import java.util.concurrent.ThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+public class ThreadLocalAwareThreadPool extends ThreadPoolExecutor {
+
+    public ThreadLocalAwareThreadPool(int corePoolSize,
+      int maximumPoolSize,
+      long keepAliveTime,
+      TimeUnit unit,
+      BlockingQueue<Runnable> workQueue,
+      ThreadFactory threadFactory,
+      RejectedExecutionHandler handler) {
+        super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, threadFactory, handler);
+    }
+
+    @Override
+    protected void afterExecute(Runnable r, Throwable t) {
+        // Call remove on each ThreadLocal
+    }
+}

core-java-modules/core-java-concurrency-basic-2/README.md

@@ -3,10 +3,12 @@
 This module contains articles about basic Java concurrency
 
 ### Relevant Articles: 
+
 - [How to Delay Code Execution in Java](https://www.baeldung.com/java-delay-code-execution)
 - [wait and notify() Methods in Java](https://www.baeldung.com/java-wait-notify)
 - [Difference Between Wait and Sleep in Java](https://www.baeldung.com/java-wait-and-sleep)
 - [Guide to the Synchronized Keyword in Java](https://www.baeldung.com/java-synchronized)
 - [Life Cycle of a Thread in Java](https://www.baeldung.com/java-thread-lifecycle)
 - [Guide to AtomicMarkableReference](https://www.baeldung.com/java-atomicmarkablereference)
+- [Why are Local Variables Thread-Safe in Java](https://www.baeldung.com/java-local-variables-thread-safe)
 - [[<-- Prev]](/core-java-modules/core-java-concurrency-basic)

core-java-modules/core-java-console/src/main/java/com/baeldung/consoleout/ConsoleAndOut.java

@@ -0,0 +1,31 @@
+package com.baeldung.consoleout;
+
+import java.io.Console;
+
+public class ConsoleAndOut {
+    public static void main(String[] args) {
+        try {
+            printConsoleObject();
+            readPasswordFromConsole();
+        } catch (Exception ex) {
+            // Eating NullPointerExcpetion which will occur when this 
+            // program will be run from mediums other than console
+        }
+        printSysOut();    
+    }
+
+    static void printConsoleObject() {
+        Console console = System.console();
+        console.writer().print(console);
+    }
+
+    static void readPasswordFromConsole() {
+        Console console = System.console();
+        char[] password = console.readPassword("Enter password: ");
+        console.printf(String.valueOf(password));
+    }
+    
+    static void printSysOut() {
+        System.out.println(System.out);
+    }
+}

core-java-modules/core-java-console/src/test/java/com/baeldung/consoleout/ConsoleAndOutUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.consoleout;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class ConsoleAndOutUnitTest {
+
+    @Test
+    void whenRetreivingConsole_thenPrintConsoleObject() {
+        assertThrows(NullPointerException.class, () -> {
+            ConsoleAndOut.printConsoleObject();  
+        });
+    }
+    
+    @Test
+    void whenReadingPassword_thenReadPassword() {
+        assertThrows(NullPointerException.class, () -> {
+            ConsoleAndOut.readPasswordFromConsole();  
+        });
+    }
+    
+    @Test
+    void whenRetrievingSysOut_thenPrintSysOutObject() {
+        ConsoleAndOut.printSysOut();
+    }
+}

core-java-modules/core-java-exceptions-2/README.md

@@ -13,3 +13,4 @@ This module contains articles about core java exceptions
 - [Java Global Exception Handler](https://www.baeldung.com/java-global-exception-handler)
 - [How to Find an Exception’s Root Cause in Java](https://www.baeldung.com/java-exception-root-cause)
 - [Java IOException “Too many open files”](https://www.baeldung.com/java-too-many-open-files)
+- [When Does Java Throw the ExceptionInInitializerError?](https://www.baeldung.com/java-exceptionininitializererror)

core-java-modules/core-java-io-3/.gitignore

@@ -0,0 +1,2 @@
+test-link*
+0.*

core-java-modules/core-java-io-3/README.md

@@ -3,5 +3,7 @@
 This module contains articles about core Java input and output (IO)
 
 ### Relevant Articles: 
+
 - [Java – Create a File](https://www.baeldung.com/java-how-to-create-a-file)
+- [Check If a Directory Is Empty in Java](https://www.baeldung.com/java-check-empty-directory)
 - [[<-- Prev]](/core-java-modules/core-java-io-2)

core-java-modules/core-java-io-3/pom.xml

@@ -46,41 +46,14 @@
             <version>${assertj.version}</version>
             <scope>test</scope>
         </dependency>
-        <!-- https://mvnrepository.com/artifact/com.github.tomakehurst/wiremock -->
-        <dependency>
-            <groupId>com.github.tomakehurst</groupId>
-            <artifactId>wiremock</artifactId>
-            <version>${wiremock.version}</version>
-            <scope>test</scope>
-        </dependency>
 
     </dependencies>
 
     <build>
-        <finalName>core-java-io-3</finalName>
-        <resources>
-            <resource>
-                <directory>src/main/resources</directory>
-                <filtering>true</filtering>
-            </resource>
-        </resources>
-        <plugins>
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-javadoc-plugin</artifactId>
-                <version>${maven-javadoc-plugin.version}</version>
-                <configuration>
-                    <source>${maven.compiler.source}</source>
-                    <target>${maven.compiler.target}</target>
-                </configuration>
-            </plugin>
-        </plugins>
     </build>
 
     <properties>
         <assertj.version>3.6.1</assertj.version>
-        <maven-javadoc-plugin.version>3.0.0-M1</maven-javadoc-plugin.version>
-        <wiremock.version>2.26.3</wiremock.version>
     </properties>
 
 </project>

core-java-modules/core-java-io-3/src/main/java/com/baeldung/copydirectory/ApacheCommons.java

@@ -0,0 +1,15 @@
+package com.baeldung.copydirectory;
+
+import java.io.File;
+import java.io.IOException;
+
+import org.apache.commons.io.FileUtils;
+
+public class ApacheCommons {
+
+    public static void copyDirectory(String sourceDirectoryLocation, String destinationDirectoryLocation) throws IOException {
+        File sourceDirectory = new File(sourceDirectoryLocation);
+        File destinationDirectory = new File(destinationDirectoryLocation);
+        FileUtils.copyDirectory(sourceDirectory, destinationDirectory);
+    }
+}

core-java-modules/core-java-io-3/src/main/java/com/baeldung/copydirectory/CoreOld.java

@@ -0,0 +1,38 @@
+package com.baeldung.copydirectory;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+
+public class CoreOld {
+
+    public static void copyDirectoryJavaUnder7(File source, File destination) throws IOException {
+        if (source.isDirectory()) {
+            copyDirectory(source, destination);
+        } else {
+            copyFile(source, destination);
+        }
+    }
+
+    private static void copyDirectory(File sourceDirectory, File destinationDirectory) throws IOException {
+        if (!destinationDirectory.exists()) {
+            destinationDirectory.mkdir();
+        }
+        for (String f : sourceDirectory.list()) {
+            copyDirectoryJavaUnder7(new File(sourceDirectory, f), new File(destinationDirectory, f));
+        }
+    }
+
+    private static void copyFile(File sourceFile, File destinationFile) throws IOException {
+        try (InputStream in = new FileInputStream(sourceFile); OutputStream out = new FileOutputStream(destinationFile)) {
+            byte[] buf = new byte[1024];
+            int length;
+            while ((length = in.read(buf)) > 0) {
+                out.write(buf, 0, length);
+            }
+        }
+    }
+}

core-java-modules/core-java-io-3/src/main/java/com/baeldung/copydirectory/JavaNio.java

@@ -0,0 +1,22 @@
+package com.baeldung.copydirectory;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+
+public class JavaNio {
+
+    public static void copyDirectory(String sourceDirectoryLocation, String destinationDirectoryLocation) throws IOException {
+        Files.walk(Paths.get(sourceDirectoryLocation))
+          .forEach(source -> {
+              Path destination = Paths.get(destinationDirectoryLocation, source.toString()
+                .substring(sourceDirectoryLocation.length()));
+              try {
+                  Files.copy(source, destination);
+              } catch (IOException e) {
+                  e.printStackTrace();
+              }
+          });
+    }
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/copydirectory/ApacheCommonsUnitTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.copydirectory;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Comparator;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class ApacheCommonsUnitTest {
+
+    private final String sourceDirectoryLocation = "src/test/resources/sourceDirectory3";
+    private final String subDirectoryName = "/childDirectory";
+    private final String fileName = "/file.txt";
+    private final String destinationDirectoryLocation = "src/test/resources/destinationDirectory3";
+
+    @BeforeEach
+    public void createDirectoryWithSubdirectoryAndFile() throws IOException {
+        Files.createDirectories(Paths.get(sourceDirectoryLocation));
+        Files.createDirectories(Paths.get(sourceDirectoryLocation + subDirectoryName));
+        Files.createFile(Paths.get(sourceDirectoryLocation + subDirectoryName + fileName));
+    }
+
+    @Test
+    public void whenSourceDirectoryExists_thenDirectoryIsFullyCopied() throws IOException {
+        ApacheCommons.copyDirectory(sourceDirectoryLocation, destinationDirectoryLocation);
+
+        assertTrue(new File(destinationDirectoryLocation).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName + fileName).exists());
+    }
+
+    @Test
+    public void whenSourceDirectoryDoesNotExist_thenExceptionIsThrown() {
+        assertThrows(Exception.class, () -> ApacheCommons.copyDirectory("nonExistingDirectory", destinationDirectoryLocation));
+    }
+
+    @AfterEach
+    public void cleanUp() throws IOException {
+        Files.walk(Paths.get(sourceDirectoryLocation))
+            .sorted(Comparator.reverseOrder())
+            .map(Path::toFile)
+            .forEach(File::delete);
+        if (new File(destinationDirectoryLocation).exists()) {
+            Files.walk(Paths.get(destinationDirectoryLocation))
+                .sorted(Comparator.reverseOrder())
+                .map(Path::toFile)
+                .forEach(File::delete);
+        }
+    }
+
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/copydirectory/CoreOldUnitTest.java

@@ -0,0 +1,63 @@
+package com.baeldung.copydirectory;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Comparator;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class CoreOldUnitTest {
+
+    private final String sourceDirectoryLocation = "src/test/resources/sourceDirectory1";
+    private final String subDirectoryName = "/childDirectory";
+    private final String fileName = "/file.txt";
+    private final String destinationDirectoryLocation = "src/test/resources/destinationDirectory1";
+
+    @BeforeEach
+    public void createDirectoryWithSubdirectoryAndFile() throws IOException {
+        Files.createDirectories(Paths.get(sourceDirectoryLocation));
+        Files.createDirectories(Paths.get(sourceDirectoryLocation + subDirectoryName));
+        Files.createFile(Paths.get(sourceDirectoryLocation + subDirectoryName + fileName));
+    }
+
+    @Test
+    public void whenSourceDirectoryExists_thenDirectoryIsFullyCopied() throws IOException {
+        File sourceDirectory = new File(sourceDirectoryLocation);
+        File destinationDirectory = new File(destinationDirectoryLocation);
+        CoreOld.copyDirectoryJavaUnder7(sourceDirectory, destinationDirectory);
+
+        assertTrue(new File(destinationDirectoryLocation).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName + fileName).exists());
+    }
+
+    @Test
+    public void whenSourceDirectoryDoesNotExist_thenExceptionIsThrown() throws IOException {
+        File sourceDirectory = new File("nonExistingDirectory");
+        File destinationDirectory = new File(destinationDirectoryLocation);
+        assertThrows(IOException.class, () -> CoreOld.copyDirectoryJavaUnder7(sourceDirectory, destinationDirectory));
+    }
+
+    @AfterEach
+    public void cleanUp() throws IOException {
+        Files.walk(Paths.get(sourceDirectoryLocation))
+            .sorted(Comparator.reverseOrder())
+            .map(Path::toFile)
+            .forEach(File::delete);
+        if (new File(destinationDirectoryLocation).exists()) {
+            Files.walk(Paths.get(destinationDirectoryLocation))
+                .sorted(Comparator.reverseOrder())
+                .map(Path::toFile)
+                .forEach(File::delete);
+        }
+    }
+
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/copydirectory/JavaNioUnitTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.copydirectory;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.Comparator;
+
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class JavaNioUnitTest {
+
+    private final String sourceDirectoryLocation = "src/test/resources/sourceDirectory2";
+    private final String subDirectoryName = "/childDirectory";
+    private final String fileName = "/file.txt";
+    private final String destinationDirectoryLocation = "src/test/resources/destinationDirectory2";
+
+    @BeforeEach
+    public void createDirectoryWithSubdirectoryAndFile() throws IOException {
+        Files.createDirectories(Paths.get(sourceDirectoryLocation));
+        Files.createDirectories(Paths.get(sourceDirectoryLocation + subDirectoryName));
+        Files.createFile(Paths.get(sourceDirectoryLocation + subDirectoryName + fileName));
+    }
+
+    @Test
+    public void whenSourceDirectoryExists_thenDirectoryIsFullyCopied() throws IOException {
+        JavaNio.copyDirectory(sourceDirectoryLocation, destinationDirectoryLocation);
+
+        assertTrue(new File(destinationDirectoryLocation).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName).exists());
+        assertTrue(new File(destinationDirectoryLocation + subDirectoryName + fileName).exists());
+    }
+
+    @Test
+    public void whenSourceDirectoryDoesNotExist_thenExceptionIsThrown() {
+        assertThrows(IOException.class, () -> JavaNio.copyDirectory("nonExistingDirectory", destinationDirectoryLocation));
+    }
+
+    @AfterEach
+    public void cleanUp() throws IOException {
+        Files.walk(Paths.get(sourceDirectoryLocation))
+            .sorted(Comparator.reverseOrder())
+            .map(Path::toFile)
+            .forEach(File::delete);
+        if (new File(destinationDirectoryLocation).exists()) {
+            Files.walk(Paths.get(destinationDirectoryLocation))
+                .sorted(Comparator.reverseOrder())
+                .map(Path::toFile)
+                .forEach(File::delete);
+        }
+    }
+
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/existence/ExistenceUnitTest.java

@@ -0,0 +1,91 @@
+package com.baeldung.existence;
+
+import org.junit.Test;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.LinkOption;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.concurrent.ThreadLocalRandom;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+public class ExistenceUnitTest {
+
+    @Test
+    public void givenFile_whenDoesNotExist_thenFilesReturnsFalse() {
+        Path path = Paths.get("does-not-exist.txt");
+
+        assertFalse(Files.exists(path));
+        assertTrue(Files.notExists(path));
+    }
+
+    @Test
+    public void givenFile_whenExists_thenFilesShouldReturnTrue() throws IOException {
+        Path tempFile = Files.createTempFile("baeldung", "exist-nio");
+        assertTrue(Files.exists(tempFile));
+        assertFalse(Files.notExists(tempFile));
+
+        Path tempDirectory = Files.createTempDirectory("baeldung-exists");
+        assertTrue(Files.exists(tempDirectory));
+        assertFalse(Files.notExists(tempDirectory));
+
+        assertTrue(Files.isDirectory(tempDirectory));
+        assertFalse(Files.isDirectory(tempFile));
+        assertTrue(Files.isRegularFile(tempFile));
+
+        assertTrue(Files.isReadable(tempFile));
+
+        Files.deleteIfExists(tempFile);
+        Files.deleteIfExists(tempDirectory);
+    }
+
+    @Test
+    public void givenSymbolicLink_whenTargetDoesNotExists_thenFollowOrNotBasedOnTheOptions() throws IOException {
+        Path target = Files.createTempFile("baeldung", "target");
+        Path symbol = Paths.get("test-link-" + ThreadLocalRandom.current().nextInt());
+
+        Path symbolicLink = Files.createSymbolicLink(symbol, target);
+        assertTrue(Files.exists(symbolicLink));
+        assertTrue(Files.isSymbolicLink(symbolicLink));
+        assertFalse(Files.isSymbolicLink(target));
+
+        Files.deleteIfExists(target);
+        assertFalse(Files.exists(symbolicLink));
+        assertTrue(Files.exists(symbolicLink, LinkOption.NOFOLLOW_LINKS));
+
+        Files.deleteIfExists(symbolicLink);
+    }
+
+    @Test
+    public void givenFile_whenDoesNotExist_thenFileReturnsFalse() {
+        assertFalse(new File("invalid").exists());
+        assertFalse(new File("invalid").isFile());
+    }
+
+    @Test
+    public void givenFile_whenExist_thenShouldReturnTrue() throws IOException {
+        Path tempFilePath = Files.createTempFile("baeldung", "exist-io");
+        Path tempDirectoryPath = Files.createTempDirectory("baeldung-exists-io");
+
+        File tempFile = new File(tempFilePath.toString());
+        File tempDirectory = new File(tempDirectoryPath.toString());
+
+        assertTrue(tempFile.exists());
+        assertTrue(tempDirectory.exists());
+
+        assertTrue(tempFile.isFile());
+        assertFalse(tempDirectory.isFile());
+
+        assertTrue(tempDirectory.isDirectory());
+        assertFalse(tempFile.isDirectory());
+
+        assertTrue(tempFile.canRead());
+
+        Files.deleteIfExists(tempFilePath);
+        Files.deleteIfExists(tempDirectoryPath);
+    }
+}

core-java-modules/core-java-io-3/src/test/java/com/baeldung/openoptions/OpenOptionsUnitTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.openoptions;
+
+import org.hamcrest.CoreMatchers;
+import org.junit.AfterClass;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.io.*;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardOpenOption;
+
+import static org.junit.Assert.*;
+
+public class OpenOptionsUnitTest {
+
+    private static final String HOME = System.getProperty("user.home");
+    private static final String DUMMY_FILE_NAME = "sample.txt";
+    private static final String EXISTING_FILE_NAME = "existingFile.txt";
+
+    private static final String DUMMY_TEXT = "This is a sample text.";
+    private static final String ANOTHER_DUMMY_TEXT = "This is a another text.";
+
+    @BeforeClass
+    public static void beforeAll() throws IOException {
+        Path path = Paths.get(HOME, DUMMY_FILE_NAME);
+
+        try (OutputStream out = Files.newOutputStream(path)) {
+            out.write(DUMMY_TEXT.getBytes());
+        }
+
+        Files.createFile(Paths.get(HOME, EXISTING_FILE_NAME));
+    }
+
+    @AfterClass
+    public static void afterAll() throws IOException {
+        Files.delete(Paths.get(HOME, "newfile.txt"));
+        Files.delete(Paths.get(HOME, "sparse.txt"));
+        Files.delete(Paths.get(HOME, DUMMY_FILE_NAME));
+    }
+
+    @Test
+    public void givenExistingPath_whenCreateNewFile_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, "newfile.txt");
+        assertFalse(Files.exists(path));
+
+        Files.write(path, DUMMY_TEXT.getBytes(), StandardOpenOption.CREATE);
+        assertTrue(Files.exists(path));
+    }
+
+    @Test
+    public void givenExistingPath_whenReadExistingFile_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, DUMMY_FILE_NAME);
+
+        try (InputStream in = Files.newInputStream(path); BufferedReader reader = new BufferedReader(new InputStreamReader(in))) {
+            String line;
+            while ((line = reader.readLine()) != null) {
+                assertThat(line, CoreMatchers.containsString(DUMMY_TEXT));
+            }
+        }
+    }
+
+    @Test
+    public void givenExistingPath_whenWriteToExistingFile_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, DUMMY_FILE_NAME);
+
+        try (OutputStream out = Files.newOutputStream(path, StandardOpenOption.APPEND, StandardOpenOption.WRITE)) {
+            out.write(ANOTHER_DUMMY_TEXT.getBytes());
+        }
+    }
+
+    @Test
+    public void givenExistingPath_whenCreateSparseFile_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, "sparse.txt");
+        Files.write(path, DUMMY_TEXT.getBytes(), StandardOpenOption.CREATE_NEW, StandardOpenOption.SPARSE);
+    }
+
+    @Test
+    public void givenExistingPath_whenDeleteOnClose_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, EXISTING_FILE_NAME);
+        assertTrue(Files.exists(path)); // file was already created and exists
+
+        try (OutputStream out = Files.newOutputStream(path, StandardOpenOption.APPEND, StandardOpenOption.WRITE, StandardOpenOption.DELETE_ON_CLOSE)) {
+            out.write(ANOTHER_DUMMY_TEXT.getBytes());
+        }
+
+        assertFalse(Files.exists(path)); // file is deleted
+    }
+
+    @Test
+    public void givenExistingPath_whenWriteAndSync_thenCorrect() throws IOException {
+        Path path = Paths.get(HOME, DUMMY_FILE_NAME);
+        Files.write(path, ANOTHER_DUMMY_TEXT.getBytes(), StandardOpenOption.APPEND, StandardOpenOption.WRITE, StandardOpenOption.SYNC);
+    }
+}

core-java-modules/core-java-jvm-2/README.md

@@ -9,4 +9,5 @@ This module contains articles about working with the Java Virtual Machine (JVM).
 - [Adding Shutdown Hooks for JVM Applications](https://www.baeldung.com/jvm-shutdown-hooks)
 - [boolean and boolean[] Memory Layout in the JVM](https://www.baeldung.com/jvm-boolean-memory-layout)
 - [Where Is the Array Length Stored in JVM?](https://www.baeldung.com/java-jvm-array-length)
+- [Memory Address of Objects in Java](https://www.baeldung.com/java-object-memory-address)
 - More articles: [[<-- prev]](/core-java-modules/core-java-jvm)

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/Launcher.java

@@ -0,0 +1,19 @@
+package com.baeldung.loadedclasslisting;
+
+import java.util.Arrays;
+
+public class Launcher {
+
+    public static void main(String[] args) {
+        printClassesLoadedBy("BOOTSTRAP");
+        printClassesLoadedBy("SYSTEM");
+        printClassesLoadedBy("EXTENSION");
+    }
+
+    private static void printClassesLoadedBy(String classLoaderType) {
+        System.out.println(classLoaderType + " ClassLoader : ");
+        Class<?>[] classes = ListLoadedClassesAgent.listLoadedClasses(classLoaderType);
+        Arrays.asList(classes)
+            .forEach(clazz -> System.out.println(clazz.getCanonicalName()));
+    }
+}

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/ListLoadedClassesAgent.java

@@ -0,0 +1,40 @@
+package com.baeldung.loadedclasslisting;
+
+import java.lang.instrument.Instrumentation;
+
+public class ListLoadedClassesAgent {
+
+    private static Instrumentation instrumentation;
+
+    public static void premain(String agentArgs, Instrumentation instrumentation) {
+        ListLoadedClassesAgent.instrumentation = instrumentation;
+    }
+
+    public static Class<?>[] listLoadedClasses(String classLoaderType) {
+        if (instrumentation == null) {
+            throw new IllegalStateException(
+              "ListLoadedClassesAgent is not initialized.");
+        }
+        return instrumentation.getInitiatedClasses(
+          getClassLoader(classLoaderType));
+    }
+
+    private static ClassLoader getClassLoader(String classLoaderType) {
+        ClassLoader classLoader = null;
+        switch (classLoaderType) {
+        case "SYSTEM":
+            classLoader = ClassLoader.getSystemClassLoader();
+            break;
+        case "EXTENSION":
+            classLoader = ClassLoader.getSystemClassLoader().getParent();
+            break;
+        // passing a null value to the Instrumentation : getInitiatedClasses method
+        // defaults to the bootstrap class loader
+        case "BOOTSTRAP":
+            break;
+        default:
+            break;
+        }
+        return classLoader;
+    }
+}

core-java-modules/core-java-jvm-2/src/main/java/com/baeldung/loadedclasslisting/MANIFEST.MF

@@ -0,0 +1 @@
+Premain-Class: com.baeldung.loadedclasslisting.ListLoadedClassesAgent

core-java-modules/core-java-lambdas/src/main/java/com/baeldung/java8/entity/Human.java

@@ -37,7 +37,7 @@ public class Human {
 
     public static int compareByNameThenAge(final Human lhs, final Human rhs) {
         if (lhs.name.equals(rhs.name)) {
-            return lhs.age - rhs.age;
+            return Integer.compare(lhs.age, rhs.age);
         } else {
             return lhs.name.compareTo(rhs.name);
         }

core-java-modules/core-java-lambdas/src/test/java/com/baeldung/java8/Java8SortUnitTest.java

@@ -54,7 +54,7 @@ public class Java8SortUnitTest {
         final List<Human> humans = Lists.newArrayList(new Human("Sarah", 12), new Human("Sarah", 10), new Human("Zack", 12));
         humans.sort((lhs, rhs) -> {
             if (lhs.getName().equals(rhs.getName())) {
-                return lhs.getAge() - rhs.getAge();
+                return Integer.compare(lhs.getAge(), rhs.getAge());
             } else {
                 return lhs.getName().compareTo(rhs.getName());
             }

core-java-modules/core-java-lang-3/README.md

@@ -3,4 +3,5 @@
 This module contains articles about core features in the Java language
 
 - [Class.isInstance vs Class.isAssignableFrom](https://www.baeldung.com/java-isinstance-isassignablefrom)
+- [Converting a Java String Into a Boolean](https://www.baeldung.com/java-string-to-boolean)
 - [[<-- Prev]](/core-java-modules/core-java-lang-2)

core-java-modules/core-java-lang-oop-types/pom.xml

@@ -12,4 +12,12 @@
     <artifactId>core-java-lang-oop-types</artifactId>
     <name>core-java-lang-oop-types</name>
     <packaging>jar</packaging>
+    
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+    </dependencies>
 </project>

core-java-modules/core-java-lang-oop-types/src/main/java/com/baeldung/primitivetype/PrimitiveTypeUtil.java

@@ -0,0 +1,26 @@
+package com.baeldung.primitivetype;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class PrimitiveTypeUtil {
+
+    private static final Map<Class<?>, Class<?>> WRAPPER_TYPE_MAP;
+    static {
+        WRAPPER_TYPE_MAP = new HashMap<Class<?>, Class<?>>(16);
+        WRAPPER_TYPE_MAP.put(Integer.class, int.class);
+        WRAPPER_TYPE_MAP.put(Byte.class, byte.class);
+        WRAPPER_TYPE_MAP.put(Character.class, char.class);
+        WRAPPER_TYPE_MAP.put(Boolean.class, boolean.class);
+        WRAPPER_TYPE_MAP.put(Double.class, double.class);
+        WRAPPER_TYPE_MAP.put(Float.class, float.class);
+        WRAPPER_TYPE_MAP.put(Long.class, long.class);
+        WRAPPER_TYPE_MAP.put(Short.class, short.class);
+        WRAPPER_TYPE_MAP.put(Void.class, void.class);
+    }
+
+    public static boolean isPrimitiveType(Object source) {
+        return WRAPPER_TYPE_MAP.containsKey(source.getClass());
+    }
+
+}

core-java-modules/core-java-lang-oop-types/src/test/java/com/baeldung/primitivetype/PrimitiveTypeUnitTest.java

@@ -0,0 +1,34 @@
+package com.baeldung.primitivetype;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.apache.commons.lang3.ClassUtils;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.Test;
+
+import com.google.common.primitives.Primitives;
+
+public class PrimitiveTypeUnitTest {
+
+    @Test
+    public void givenAClass_whenCheckWithPrimitiveTypeUtil_thenShouldValidate() {
+        assertTrue(PrimitiveTypeUtil.isPrimitiveType(false));
+        assertTrue(PrimitiveTypeUtil.isPrimitiveType(1L));
+        assertFalse(PrimitiveTypeUtil.isPrimitiveType(StringUtils.EMPTY));
+    }
+
+    @Test
+    public void givenAClass_whenCheckWithCommonsLang_thenShouldValidate() {
+        assertTrue(ClassUtils.isPrimitiveOrWrapper(Boolean.FALSE.getClass()));
+        assertTrue(ClassUtils.isPrimitiveOrWrapper(boolean.class));
+        assertFalse(ClassUtils.isPrimitiveOrWrapper(StringUtils.EMPTY.getClass()));
+    }
+
+    @Test
+    public void givenAClass_whenCheckWithGuava_thenShouldValidate() {
+        assertTrue(Primitives.isWrapperType(Boolean.FALSE.getClass()));
+        assertFalse(Primitives.isWrapperType(StringUtils.EMPTY.getClass()));
+        assertFalse(Primitives.isWrapperType(Boolean.TYPE.getClass()));
+    }
+}

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparable/Player.java

@@ -45,7 +45,7 @@ public class Player implements Comparable<Player> {
 
     @Override
     public int compareTo(Player otherPlayer) {
-        return (this.getRanking() - otherPlayer.getRanking());
+        return Integer.compare(getRanking(), otherPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerAgeComparator.java

@@ -6,7 +6,7 @@ public class PlayerAgeComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getAge() - secondPlayer.getAge());
+       return Integer.compare(firstPlayer.getAge(), secondPlayer.getAge());
     }
 
 }

core-java-modules/core-java-lang/src/main/java/com/baeldung/comparator/PlayerRankingComparator.java

@@ -6,7 +6,7 @@ public class PlayerRankingComparator implements Comparator<Player> {
 
     @Override
     public int compare(Player firstPlayer, Player secondPlayer) {
-       return (firstPlayer.getRanking() - secondPlayer.getRanking());
+       return Integer.compare(firstPlayer.getRanking(), secondPlayer.getRanking());
     }
 
 }

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/AvoidingSubtractionUnitTest.java

@@ -0,0 +1,26 @@
+package com.baeldung.comparator;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+import static org.junit.Assert.assertEquals;
+
+public class AvoidingSubtractionUnitTest {
+
+    @Test
+    public void givenTwoPlayers_whenUsingSubtraction_thenOverflow() {
+        Comparator<Player> comparator = (p1, p2) -> p1.getRanking() - p2.getRanking();
+        Player player1 = new Player(59, "John", Integer.MAX_VALUE);
+        Player player2 = new Player(67, "Roger", -1);
+
+        List<Player> players = Arrays.asList(player1, player2);
+        players.sort(comparator);
+        System.out.println(players);
+
+        assertEquals("John", players.get(0).getName());
+        assertEquals("Roger", players.get(1).getName());
+    }
+}

core-java-modules/core-java-lang/src/test/java/com/baeldung/comparator/Java8ComparatorUnitTest.java

@@ -1,14 +1,14 @@
 package com.baeldung.comparator;
 
-import static org.junit.Assert.assertEquals;
+import org.junit.Before;
+import org.junit.Test;
 
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
 
-import org.junit.Before;
+import static org.junit.Assert.assertEquals;
-import org.junit.Test;
 
 public class Java8ComparatorUnitTest {
 
@@ -28,7 +28,7 @@ public class Java8ComparatorUnitTest {
     @Test
     public void whenComparing_UsingLambda_thenSorted() {
         System.out.println("************** Java 8 Comaparator **************");
-        Comparator<Player> byRanking = (Player player1, Player player2) -> player1.getRanking() - player2.getRanking();
+        Comparator<Player> byRanking = (Player player1, Player player2) -> Integer.compare(player1.getRanking(), player2.getRanking());
 
         System.out.println("Before Sorting : " + footballTeam);
         Collections.sort(footballTeam, byRanking);

core-java-modules/core-java-nio-2/src/main/java/com/baeldung/selector/EchoServer.java

@@ -49,11 +49,11 @@ public class EchoServer {
         if (new String(buffer.array()).trim().equals(POISON_PILL)) {
             client.close();
             System.out.println("Not accepting client messages anymore");
+        } else {
+            buffer.flip();
+            client.write(buffer);
+            buffer.clear();
         }
-
-        buffer.flip();
-        client.write(buffer);
-        buffer.clear();
     }
 
     private static void register(Selector selector, ServerSocketChannel serverSocket) throws IOException {

core-java-modules/core-java-os/src/test/java/com/baeldung/screenshot/ScreenshotUnitTest.java

@@ -0,0 +1,51 @@
+import javax.imageio.ImageIO;
+import java.awt.Component;
+import java.awt.GraphicsDevice;
+import java.awt.GraphicsEnvironment;
+import java.awt.Rectangle;
+import java.awt.Robot;
+import java.awt.Toolkit;
+import java.awt.image.BufferedImage;
+import java.io.File;
+import org.junit.Test;
+
+import static org.junit.Assert.assertTrue;
+
+public class ScreenshotUnitTest {
+
+    @Test
+    public void givenMainScreen_whenTakeScreenshot_thenSaveToFile() throws Exception {
+        Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());
+        BufferedImage capture = new Robot().createScreenCapture(screenRect);
+        File imageFile = File.createTempFile("single-screen", "bmp");
+        ImageIO.write(capture, "bmp", imageFile);
+        assertTrue(imageFile.exists());
+    }
+
+    @Test
+    public void givenMultipleScreens_whenTakeScreenshot_thenSaveToFile() throws Exception {
+        GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
+        GraphicsDevice[] screens = ge.getScreenDevices();
+        Rectangle allScreenBounds = new Rectangle();
+        for (GraphicsDevice screen : screens) {
+            Rectangle screenBounds = screen.getDefaultConfiguration().getBounds();
+            allScreenBounds.width += screenBounds.width;
+            allScreenBounds.height = Math.max(allScreenBounds.height, screenBounds.height);
+        }
+        BufferedImage capture = new Robot().createScreenCapture(allScreenBounds);
+        File imageFile = File.createTempFile("all-screens", "bmp");
+        ImageIO.write(capture, "bmp", imageFile);
+        assertTrue(imageFile.exists());
+    }
+
+    @Test
+    public void givenComponent_whenTakeScreenshot_thenSaveToFile(Component component) throws Exception {
+        Rectangle componentRect = component.getBounds();
+        BufferedImage bufferedImage = new BufferedImage(componentRect.width, componentRect.height, BufferedImage.TYPE_INT_ARGB);
+        component.paint(bufferedImage.getGraphics());
+        File imageFile = File.createTempFile("component-screenshot", "bmp");
+        ImageIO.write(bufferedImage, "bmp", imageFile);
+        assertTrue(imageFile.exists());
+    }
+
+}

core-java-modules/core-java-regex/src/test/java/com/baeldung/regex/countmatches/CountMatchesUnitTest.java

@@ -1,12 +1,11 @@
 package com.baeldung.regex.countmatches;
 
-import static org.junit.Assert.assertNotEquals;
+import org.junit.Test;
-import static org.junit.jupiter.api.Assertions.assertEquals;
 
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
 
-import org.junit.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
 
 /**
  * Unit Test intended to count number of matches of a RegEx using Java 8 and 9.
@@ -65,7 +64,7 @@ public class CountMatchesUnitTest {
             count++;
         }
 
-        assertNotEquals(3, count);
+        assertEquals(2, count);
     }
 
     @Test

core-java-modules/core-java-security-2/README.md

@@ -9,4 +9,5 @@ This module contains articles about core Java Security
 - [Hashing a Password in Java](https://www.baeldung.com/java-password-hashing)
 - [SHA-256 and SHA3-256 Hashing in Java](https://www.baeldung.com/sha-256-hashing-java)
 - [Checksums in Java](https://www.baeldung.com/java-checksums)
+- [How to Read PEM File to Get Public and Private Keys](https://www.baeldung.com/java-read-pem-file-keys)
 - More articles: [[<-- prev]](/core-java-modules/core-java-security)

core-java-modules/core-java/README.md

@@ -1,13 +1,13 @@
 ## Core Java Cookbooks and Examples
 
 ### Relevant Articles: 
-[Getting Started with Java Properties](http://www.baeldung.com/java-properties)
+- [Getting Started with Java Properties](http://www.baeldung.com/java-properties)
-[Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
+- [Java Money and the Currency API](http://www.baeldung.com/java-money-and-currency)
-[Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
+- [Introduction to Java Serialization](http://www.baeldung.com/java-serialization)
-[Guide to UUID in Java](http://www.baeldung.com/java-uuid)
+- [Guide to UUID in Java](http://www.baeldung.com/java-uuid)
-[Compiling Java *.class Files with javac](http://www.baeldung.com/javac)
+- [Compiling Java *.class Files with javac](http://www.baeldung.com/javac)
-[Introduction to Javadoc](http://www.baeldung.com/javadoc)
+- [Introduction to Javadoc](http://www.baeldung.com/javadoc)
-[Guide to the Externalizable Interface in Java](http://www.baeldung.com/java-externalizable)
+- [Guide to the Externalizable Interface in Java](http://www.baeldung.com/java-externalizable)
-[What is the serialVersionUID?](http://www.baeldung.com/java-serial-version-uid)
+- [What is the serialVersionUID?](http://www.baeldung.com/java-serial-version-uid)
-[A Guide to the ResourceBundle](http://www.baeldung.com/java-resourcebundle)
+- [A Guide to the ResourceBundle](http://www.baeldung.com/java-resourcebundle)
-[Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)
+- [Merging java.util.Properties Objects](https://www.baeldung.com/java-merging-properties)

core-java-modules/pom.xml

@@ -22,6 +22,7 @@
         <!-- <module>core-java-11</module> --> <!-- We haven't upgraded to java 11. Fixing in BAEL-10841 -->
         <!-- <module>core-java-12</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
         <!-- <module>core-java-13</module> --> <!-- We haven't upgraded to java 12. Fixing in BAEL-10841 -->
+        <!-- <module>core-java-14</module> --> <!-- We haven't upgraded to java 14.-->
         <module>core-java-8</module>
         <module>core-java-8-2</module>
 
@@ -59,11 +60,16 @@
         <module>core-java-concurrency-basic</module>
         <module>core-java-concurrency-basic-2</module>
         <module>core-java-concurrency-collections</module>
+        <module>core-java-concurrency-collections-2</module>
+        <module>core-java-console</module>
 
+        <!--<module>core-java-8-datetime</module>--> <!-- unit test case failure -->
+        <module>core-java-8-datetime-2</module>
         <!-- <module>core-java-date-operations-1</module> --> <!-- We haven't upgraded to java 9. Fixing in BAEL-10841 -->
         <module>core-java-date-operations-2</module>
         <!-- We haven't upgraded to java 9. -->
         <!-- <module>core-java-datetime-computations</module> <module>core-java-datetime-conversion</module> <module>core-java-datetime-java8</module> <module>core-java-datetime-string</module> -->
+        <module>core-java-8-datetime</module>
 
         <module>core-java-exceptions</module>
         <module>core-java-exceptions-2</module>

core-kotlin-modules/core-kotlin-collections/README.md

@@ -3,6 +3,7 @@
 This module contains articles about core Kotlin collections.
 
 ### Relevant articles:
+
 - [Split a List Into Parts in Kotlin](https://www.baeldung.com/kotlin-split-list-into-parts)
 - [Finding an Element in a List Using Kotlin](https://www.baeldung.com/kotlin-finding-element-in-list)
 - [Overview of Kotlin Collections API](https://www.baeldung.com/kotlin-collections-api)
@@ -12,3 +13,4 @@ This module contains articles about core Kotlin collections.
 - [Difference between fold and reduce in Kotlin](https://www.baeldung.com/kotlin/fold-vs-reduce)
 - [Guide to Sorting in Kotlin](https://www.baeldung.com/kotlin-sort)
 - [Working With Lists in Kotlin](https://www.baeldung.com/kotlin/lists)
+- [Iterating Collections by Index in Kotlin](https://www.baeldung.com/kotlin/iterating-collections-by-index)

core-kotlin-modules/core-kotlin-lang-oop-2/README.md

@@ -7,4 +7,5 @@ This module contains articles about Object-Oriented Programming in Kotlin
 - [Generics in Kotlin](https://www.baeldung.com/kotlin-generics)
 - [Delegated Properties in Kotlin](https://www.baeldung.com/kotlin-delegated-properties)
 - [Delegation Pattern in Kotlin](https://www.baeldung.com/kotlin-delegation-pattern)
+- [Anonymous Inner Classes in Kotlin](https://www.baeldung.com/kotlin/anonymous-inner-classes)
 - [[<-- Prev]](/core-kotlin-modules/core-kotlin-lang-oop)

core-kotlin-modules/core-kotlin/src/main/kotlin/com/baeldung/exceptionhandling/ExceptionHandling.kt

@@ -0,0 +1,88 @@
+package com.baeldung.exceptionhandling
+
+import java.io.IOException
+
+class ExceptionHandling {
+
+    fun tryCatchBlock(): Int? {
+        try {
+            val message = "Welcome to Kotlin Tutorials"
+            return message.toInt()
+        } catch (exception: NumberFormatException) {
+            println("NumberFormatException in the code")
+            return null
+        }
+    }
+
+    fun tryCatchExpression(): Int? {
+        val number = try {
+            val message = "Welcome to Kotlin Tutorials"
+            message.toInt()
+        } catch (exception: NumberFormatException) {
+            println("NumberFormatException in the code")
+            null
+        }
+        return number
+    }
+
+    fun multipleCatchBlock(): Int? {
+        return try {
+            val result = 25 / 0
+            result
+        } catch (exception: NumberFormatException) {
+            println("NumberFormatException in the code")
+            null
+        } catch (exception: ArithmeticException) {
+            println("ArithmeticException in the code")
+            null
+        } catch (exception: Exception) {
+            println("Exception in the code")
+            null
+        }
+    }
+
+    fun nestedTryCatchBlock(): Int? {
+        return try {
+            val firstNumber = 50 / 2 * 0
+            try {
+                val secondNumber = 100 / firstNumber
+                secondNumber
+            } catch (exception: ArithmeticException) {
+                println("ArithmeticException in the code")
+                null
+            }
+        } catch (exception: NumberFormatException) {
+            println("NumberFormatException in the code")
+            null
+        }
+    }
+
+    fun finallyBlock(): Int? {
+        return try {
+            val message = "Welcome to Kotlin Tutorials"
+            message.toInt()
+        } catch (exception: NumberFormatException) {
+            println("NumberFormatException in the code")
+            null
+        } finally {
+            println("In the Finally block")
+        }
+    }
+
+    fun throwKeyword(): Int {
+        val message = "Welcome to Kotlin Tutorials"
+        if (message.length > 10) throw IllegalArgumentException("String is invalid")
+        else return message.length
+    }
+
+    fun throwExpression(): Int? {
+        val message: String? = null
+        return message?.length ?: throw IllegalArgumentException("String is null")
+    }
+
+    @Throws(IOException::class)
+    fun throwsAnnotation(): String?{
+        val filePath = null
+        return filePath ?: throw IOException("File path is invalid")
+    }
+}

core-kotlin-modules/core-kotlin/src/test/kotlin/com/baeldung/exceptionhandling/ExceptionHandlingUnitTest.kt

@@ -0,0 +1,51 @@
+package com.baeldung.exceptionhandling
+
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.assertThrows
+import java.io.IOException
+import kotlin.test.assertNull
+
+class ExceptionHandlingUnitTest {
+
+    private val classUnderTest: ExceptionHandling = ExceptionHandling()
+
+    @Test
+    fun givenInvalidConversion_whenTryCatchUsed_thenReturnsCatchBlockValue(){
+        assertNull(classUnderTest.tryCatchBlock())
+    }
+
+    @Test
+    fun givenInvalidConversion_whenTryCatchExpressionUsed_thenReturnsCatchBlockValue(){
+        assertNull(classUnderTest.tryCatchExpression())
+    }
+
+    @Test
+    fun givenDivisionByZero_whenMultipleCatchUsed_thenReturnsCatchBlockValue(){
+        assertNull(classUnderTest.multipleCatchBlock())
+    }
+
+    @Test
+    fun givenDivisionByZero_whenNestedTryCatchUsed_thenReturnsNestedCatchBlockValue(){
+        assertNull(classUnderTest.nestedTryCatchBlock())
+    }
+
+    @Test
+    fun givenInvalidConversion_whenTryCatchFinallyUsed_thenReturnsCatchAndFinallyBlock(){
+        assertNull(classUnderTest.finallyBlock())
+    }
+
+    @Test
+    fun givenIllegalArgument_whenThrowKeywordUsed_thenThrowsException(){
+        assertThrows<IllegalArgumentException> { classUnderTest.throwKeyword() }
+    }
+
+    @Test
+    fun givenIllegalArgument_whenElvisExpressionUsed_thenThrowsException(){
+        assertThrows<IllegalArgumentException> { classUnderTest.throwExpression() }
+    }
+
+    @Test
+    fun whenAnnotationUsed_thenThrowsException(){
+        assertThrows<IOException> { classUnderTest.throwsAnnotation() }
+    }
+}

deeplearning4j/pom.xml

@@ -37,6 +37,16 @@
             <artifactId>deeplearning4j-nn</artifactId>
             <version>${dl4j.version}</version>
         </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-api</artifactId>
+            <version>${slf4j.version}</version>
+        </dependency>
+        <dependency>
+            <groupId>org.slf4j</groupId>
+            <artifactId>slf4j-log4j12</artifactId>
+            <version>${slf4j.version}</version>
+        </dependency>
         <!-- https://mvnrepository.com/artifact/org.datavec/datavec-api -->
         <dependency>
             <groupId>org.datavec</groupId>
@@ -53,6 +63,7 @@
     <properties>
         <dl4j.version>0.9.1</dl4j.version> <!-- Latest non beta version -->
         <httpclient.version>4.3.5</httpclient.version>
+        <slf4j.version>1.7.5</slf4j.version>
     </properties>
 
 </project>

deeplearning4j/src/main/java/com/baeldung/deeplearning4j/cnn/CifarDataSetService.java

@@ -0,0 +1,47 @@
+package com.baeldung.deeplearning4j.cnn;
+
+import lombok.Getter;
+import org.deeplearning4j.datasets.iterator.impl.CifarDataSetIterator;
+import org.deeplearning4j.nn.conf.inputs.InputType;
+import org.nd4j.linalg.dataset.api.iterator.DataSetIterator;
+
+import java.util.List;
+
+@Getter
+class CifarDataSetService implements IDataSetService {
+
+    private final InputType inputType = InputType.convolutional(32, 32, 3);
+    private final int trainImagesNum = 512;
+    private final int testImagesNum = 128;
+    private final int trainBatch = 16;
+    private final int testBatch = 8;
+
+    private final CifarDataSetIterator trainIterator;
+
+    private final CifarDataSetIterator testIterator;
+
+    CifarDataSetService() {
+        trainIterator = new CifarDataSetIterator(trainBatch, trainImagesNum, true);
+        testIterator = new CifarDataSetIterator(testBatch, testImagesNum, false);
+    }
+
+    @Override
+    public DataSetIterator trainIterator() {
+        return trainIterator;
+    }
+
+    @Override
+    public DataSetIterator testIterator() {
+        return testIterator;
+    }
+
+    @Override
+    public InputType inputType() {
+        return inputType;
+    }
+
+    @Override
+    public List<String> labels() {
+        return trainIterator.getLabels();
+    }
+}

deeplearning4j/src/main/java/com/baeldung/deeplearning4j/cnn/CnnExample.java

@@ -0,0 +1,18 @@
+package com.baeldung.deeplearning4j.cnn;
+
+
+import lombok.extern.slf4j.Slf4j;
+import org.deeplearning4j.eval.Evaluation;
+
+@Slf4j
+class CnnExample {
+
+    public static void main(String... args) {
+        CnnModel network = new CnnModel(new CifarDataSetService(), new CnnModelProperties());
+
+        network.train();
+        Evaluation evaluation = network.evaluate();
+
+        log.info(evaluation.stats());
+    }
+}

deeplearning4j/src/main/java/com/baeldung/deeplearning4j/cnn/CnnModel.java

@@ -0,0 +1,119 @@
+package com.baeldung.deeplearning4j.cnn;
+
+import lombok.extern.slf4j.Slf4j;
+import org.deeplearning4j.eval.Evaluation;
+import org.deeplearning4j.nn.api.OptimizationAlgorithm;
+import org.deeplearning4j.nn.conf.MultiLayerConfiguration;
+import org.deeplearning4j.nn.conf.NeuralNetConfiguration;
+import org.deeplearning4j.nn.conf.layers.ConvolutionLayer;
+import org.deeplearning4j.nn.conf.layers.OutputLayer;
+import org.deeplearning4j.nn.conf.layers.SubsamplingLayer;
+import org.deeplearning4j.nn.multilayer.MultiLayerNetwork;
+import org.deeplearning4j.nn.weights.WeightInit;
+import org.nd4j.linalg.activations.Activation;
+import org.nd4j.linalg.lossfunctions.LossFunctions;
+
+import java.util.stream.IntStream;
+
+@Slf4j
+class CnnModel {
+
+    private final IDataSetService dataSetService;
+
+    private final MultiLayerNetwork network;
+
+    private final CnnModelProperties properties;
+
+    CnnModel(IDataSetService dataSetService, CnnModelProperties properties) {
+
+        this.dataSetService = dataSetService;
+        this.properties = properties;
+
+        MultiLayerConfiguration configuration = new NeuralNetConfiguration.Builder()
+          .seed(1611)
+          .optimizationAlgo(OptimizationAlgorithm.STOCHASTIC_GRADIENT_DESCENT)
+          .learningRate(properties.getLearningRate())
+          .regularization(true)
+          .updater(properties.getOptimizer())
+          .list()
+          .layer(0, conv5x5())
+          .layer(1, pooling2x2Stride2())
+          .layer(2, conv3x3Stride1Padding2())
+          .layer(3, pooling2x2Stride1())
+          .layer(4, conv3x3Stride1Padding1())
+          .layer(5, pooling2x2Stride1())
+          .layer(6, dense())
+          .pretrain(false)
+          .backprop(true)
+          .setInputType(dataSetService.inputType())
+          .build();
+
+        network = new MultiLayerNetwork(configuration);
+    }
+
+    void train() {
+        network.init();
+        int epochsNum = properties.getEpochsNum();
+        IntStream.range(1, epochsNum + 1).forEach(epoch -> {
+            log.info("Epoch {} / {}", epoch, epochsNum);
+            network.fit(dataSetService.trainIterator());
+        });
+    }
+
+    Evaluation evaluate() {
+        return network.evaluate(dataSetService.testIterator());
+    }
+
+    private ConvolutionLayer conv5x5() {
+        return new ConvolutionLayer.Builder(5, 5)
+                .nIn(3)
+                .nOut(16)
+                .stride(1, 1)
+                .padding(1, 1)
+                .weightInit(WeightInit.XAVIER_UNIFORM)
+                .activation(Activation.RELU)
+                .build();
+    }
+
+    private SubsamplingLayer pooling2x2Stride2() {
+        return new SubsamplingLayer.Builder(SubsamplingLayer.PoolingType.MAX)
+                .kernelSize(2, 2)
+                .stride(2, 2)
+                .build();
+    }
+
+    private ConvolutionLayer conv3x3Stride1Padding2() {
+        return new ConvolutionLayer.Builder(3, 3)
+                .nOut(32)
+                .stride(1, 1)
+                .padding(2, 2)
+                .weightInit(WeightInit.XAVIER_UNIFORM)
+                .activation(Activation.RELU)
+                .build();
+    }
+
+    private SubsamplingLayer pooling2x2Stride1() {
+        return new SubsamplingLayer.Builder(SubsamplingLayer.PoolingType.MAX)
+                .kernelSize(2, 2)
+                .stride(1, 1)
+                .build();
+    }
+
+    private ConvolutionLayer conv3x3Stride1Padding1() {
+        return new ConvolutionLayer.Builder(3, 3)
+                .nOut(64)
+                .stride(1, 1)
+                .padding(1, 1)
+                .weightInit(WeightInit.XAVIER_UNIFORM)
+                .activation(Activation.RELU)
+                .build();
+    }
+
+    private OutputLayer dense() {
+        return new OutputLayer.Builder(LossFunctions.LossFunction.MEAN_SQUARED_LOGARITHMIC_ERROR)
+                .activation(Activation.SOFTMAX)
+                .weightInit(WeightInit.XAVIER_UNIFORM)
+                .nOut(dataSetService.labels().size() - 1)
+                .build();
+    }
+}

deeplearning4j/src/main/java/com/baeldung/deeplearning4j/cnn/CnnModelProperties.java

@@ -0,0 +1,13 @@
+package com.baeldung.deeplearning4j.cnn;
+
+import lombok.Value;
+import org.deeplearning4j.nn.conf.Updater;
+
+@Value
+class CnnModelProperties {
+    private final int epochsNum = 512;
+
+    private final double learningRate = 0.001;
+
+    private final Updater optimizer = Updater.ADAM;
+}

deeplearning4j/src/main/java/com/baeldung/deeplearning4j/cnn/IDataSetService.java

@@ -0,0 +1,16 @@
+package com.baeldung.deeplearning4j.cnn;
+
+import org.deeplearning4j.nn.conf.inputs.InputType;
+import org.nd4j.linalg.dataset.api.iterator.DataSetIterator;
+
+import java.util.List;
+
+interface IDataSetService {
+    DataSetIterator trainIterator();
+
+    DataSetIterator testIterator();
+
+    InputType inputType();
+
+    List<String> labels();
+}

docker/docker-spring-boot/README.md

@@ -0,0 +1,3 @@
+### Relevant Article:
+
+- [Creating Docker Images with Spring Boot](https://www.baeldung.com/spring-boot-docker-images)

docker/docker-spring-boot/mvnw

@@ -0,0 +1,310 @@
+#!/bin/sh
+# ----------------------------------------------------------------------------
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+# ----------------------------------------------------------------------------
+
+# ----------------------------------------------------------------------------
+# Maven Start Up Batch script
+#
+# Required ENV vars:
+# ------------------
+#   JAVA_HOME - location of a JDK home dir
+#
+# Optional ENV vars
+# -----------------
+#   M2_HOME - location of maven2's installed home dir
+#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
+#     e.g. to debug Maven itself, use
+#       set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+#   MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+# ----------------------------------------------------------------------------
+
+if [ -z "$MAVEN_SKIP_RC" ] ; then
+
+  if [ -f /etc/mavenrc ] ; then
+    . /etc/mavenrc
+  fi
+
+  if [ -f "$HOME/.mavenrc" ] ; then
+    . "$HOME/.mavenrc"
+  fi
+
+fi
+
+# OS specific support.  $var _must_ be set to either true or false.
+cygwin=false;
+darwin=false;
+mingw=false
+case "`uname`" in
+  CYGWIN*) cygwin=true ;;
+  MINGW*) mingw=true;;
+  Darwin*) darwin=true
+    # Use /usr/libexec/java_home if available, otherwise fall back to /Library/Java/Home
+    # See https://developer.apple.com/library/mac/qa/qa1170/_index.html
+    if [ -z "$JAVA_HOME" ]; then
+      if [ -x "/usr/libexec/java_home" ]; then
+        export JAVA_HOME="`/usr/libexec/java_home`"
+      else
+        export JAVA_HOME="/Library/Java/Home"
+      fi
+    fi
+    ;;
+esac
+
+if [ -z "$JAVA_HOME" ] ; then
+  if [ -r /etc/gentoo-release ] ; then
+    JAVA_HOME=`java-config --jre-home`
+  fi
+fi
+
+if [ -z "$M2_HOME" ] ; then
+  ## resolve links - $0 may be a link to maven's home
+  PRG="$0"
+
+  # need this for relative symlinks
+  while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+      PRG="$link"
+    else
+      PRG="`dirname "$PRG"`/$link"
+    fi
+  done
+
+  saveddir=`pwd`
+
+  M2_HOME=`dirname "$PRG"`/..
+
+  # make it fully qualified
+  M2_HOME=`cd "$M2_HOME" && pwd`
+
+  cd "$saveddir"
+  # echo Using m2 at $M2_HOME
+fi
+
+# For Cygwin, ensure paths are in UNIX format before anything is touched
+if $cygwin ; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME=`cygpath --unix "$M2_HOME"`
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=`cygpath --unix "$JAVA_HOME"`
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=`cygpath --path --unix "$CLASSPATH"`
+fi
+
+# For Mingw, ensure paths are in UNIX format before anything is touched
+if $mingw ; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME="`(cd "$M2_HOME"; pwd)`"
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME="`(cd "$JAVA_HOME"; pwd)`"
+fi
+
+if [ -z "$JAVA_HOME" ]; then
+  javaExecutable="`which javac`"
+  if [ -n "$javaExecutable" ] && ! [ "`expr \"$javaExecutable\" : '\([^ ]*\)'`" = "no" ]; then
+    # readlink(1) is not available as standard on Solaris 10.
+    readLink=`which readlink`
+    if [ ! `expr "$readLink" : '\([^ ]*\)'` = "no" ]; then
+      if $darwin ; then
+        javaHome="`dirname \"$javaExecutable\"`"
+        javaExecutable="`cd \"$javaHome\" && pwd -P`/javac"
+      else
+        javaExecutable="`readlink -f \"$javaExecutable\"`"
+      fi
+      javaHome="`dirname \"$javaExecutable\"`"
+      javaHome=`expr "$javaHome" : '\(.*\)/bin'`
+      JAVA_HOME="$javaHome"
+      export JAVA_HOME
+    fi
+  fi
+fi
+
+if [ -z "$JAVACMD" ] ; then
+  if [ -n "$JAVA_HOME"  ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+      # IBM's JDK on AIX uses strange locations for the executables
+      JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+      JAVACMD="$JAVA_HOME/bin/java"
+    fi
+  else
+    JAVACMD="`which java`"
+  fi
+fi
+
+if [ ! -x "$JAVACMD" ] ; then
+  echo "Error: JAVA_HOME is not defined correctly." >&2
+  echo "  We cannot execute $JAVACMD" >&2
+  exit 1
+fi
+
+if [ -z "$JAVA_HOME" ] ; then
+  echo "Warning: JAVA_HOME environment variable is not set."
+fi
+
+CLASSWORLDS_LAUNCHER=org.codehaus.plexus.classworlds.launcher.Launcher
+
+# traverses directory structure from process work directory to filesystem root
+# first directory with .mvn subdirectory is considered project base directory
+find_maven_basedir() {
+
+  if [ -z "$1" ]
+  then
+    echo "Path not specified to find_maven_basedir"
+    return 1
+  fi
+
+  basedir="$1"
+  wdir="$1"
+  while [ "$wdir" != '/' ] ; do
+    if [ -d "$wdir"/.mvn ] ; then
+      basedir=$wdir
+      break
+    fi
+    # workaround for JBEAP-8937 (on Solaris 10/Sparc)
+    if [ -d "${wdir}" ]; then
+      wdir=`cd "$wdir/.."; pwd`
+    fi
+    # end of workaround
+  done
+  echo "${basedir}"
+}
+
+# concatenates all lines of a file
+concat_lines() {
+  if [ -f "$1" ]; then
+    echo "$(tr -s '\n' ' ' < "$1")"
+  fi
+}
+
+BASE_DIR=`find_maven_basedir "$(pwd)"`
+if [ -z "$BASE_DIR" ]; then
+  exit 1;
+fi
+
+##########################################################################################
+# Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+# This allows using the maven wrapper in projects that prohibit checking in binary data.
+##########################################################################################
+if [ -r "$BASE_DIR/.mvn/wrapper/maven-wrapper.jar" ]; then
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Found .mvn/wrapper/maven-wrapper.jar"
+    fi
+else
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Couldn't find .mvn/wrapper/maven-wrapper.jar, downloading it ..."
+    fi
+    if [ -n "$MVNW_REPOURL" ]; then
+      jarUrl="$MVNW_REPOURL/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    else
+      jarUrl="https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    fi
+    while IFS="=" read key value; do
+      case "$key" in (wrapperUrl) jarUrl="$value"; break ;;
+      esac
+    done < "$BASE_DIR/.mvn/wrapper/maven-wrapper.properties"
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Downloading from: $jarUrl"
+    fi
+    wrapperJarPath="$BASE_DIR/.mvn/wrapper/maven-wrapper.jar"
+    if $cygwin; then
+      wrapperJarPath=`cygpath --path --windows "$wrapperJarPath"`
+    fi
+
+    if command -v wget > /dev/null; then
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Found wget ... using wget"
+        fi
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            wget "$jarUrl" -O "$wrapperJarPath"
+        else
+            wget --http-user=$MVNW_USERNAME --http-password=$MVNW_PASSWORD "$jarUrl" -O "$wrapperJarPath"
+        fi
+    elif command -v curl > /dev/null; then
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Found curl ... using curl"
+        fi
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            curl -o "$wrapperJarPath" "$jarUrl" -f
+        else
+            curl --user $MVNW_USERNAME:$MVNW_PASSWORD -o "$wrapperJarPath" "$jarUrl" -f
+        fi
+
+    else
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Falling back to using Java to download"
+        fi
+        javaClass="$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.java"
+        # For Cygwin, switch paths to Windows format before running javac
+        if $cygwin; then
+          javaClass=`cygpath --path --windows "$javaClass"`
+        fi
+        if [ -e "$javaClass" ]; then
+            if [ ! -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
+                if [ "$MVNW_VERBOSE" = true ]; then
+                  echo " - Compiling MavenWrapperDownloader.java ..."
+                fi
+                # Compiling the Java class
+                ("$JAVA_HOME/bin/javac" "$javaClass")
+            fi
+            if [ -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
+                # Running the downloader
+                if [ "$MVNW_VERBOSE" = true ]; then
+                  echo " - Running MavenWrapperDownloader.java ..."
+                fi
+                ("$JAVA_HOME/bin/java" -cp .mvn/wrapper MavenWrapperDownloader "$MAVEN_PROJECTBASEDIR")
+            fi
+        fi
+    fi
+fi
+##########################################################################################
+# End of extension
+##########################################################################################
+
+export MAVEN_PROJECTBASEDIR=${MAVEN_BASEDIR:-"$BASE_DIR"}
+if [ "$MVNW_VERBOSE" = true ]; then
+  echo $MAVEN_PROJECTBASEDIR
+fi
+MAVEN_OPTS="$(concat_lines "$MAVEN_PROJECTBASEDIR/.mvn/jvm.config") $MAVEN_OPTS"
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME=`cygpath --path --windows "$M2_HOME"`
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=`cygpath --path --windows "$JAVA_HOME"`
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=`cygpath --path --windows "$CLASSPATH"`
+  [ -n "$MAVEN_PROJECTBASEDIR" ] &&
+    MAVEN_PROJECTBASEDIR=`cygpath --path --windows "$MAVEN_PROJECTBASEDIR"`
+fi
+
+# Provide a "standardized" way to retrieve the CLI args that will
+# work with both Windows and non-Windows executions.
+MAVEN_CMD_LINE_ARGS="$MAVEN_CONFIG $@"
+export MAVEN_CMD_LINE_ARGS
+
+WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+exec "$JAVACMD" \
+  $MAVEN_OPTS \
+  -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \
+  "-Dmaven.home=${M2_HOME}" "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \
+  ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@"

docker/docker-spring-boot/mvnw.cmd

@@ -0,0 +1,182 @@
+@REM ----------------------------------------------------------------------------
+@REM Licensed to the Apache Software Foundation (ASF) under one
+@REM or more contributor license agreements.  See the NOTICE file
+@REM distributed with this work for additional information
+@REM regarding copyright ownership.  The ASF licenses this file
+@REM to you under the Apache License, Version 2.0 (the
+@REM "License"); you may not use this file except in compliance
+@REM with the License.  You may obtain a copy of the License at
+@REM
+@REM    https://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM Unless required by applicable law or agreed to in writing,
+@REM software distributed under the License is distributed on an
+@REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+@REM KIND, either express or implied.  See the License for the
+@REM specific language governing permissions and limitations
+@REM under the License.
+@REM ----------------------------------------------------------------------------
+
+@REM ----------------------------------------------------------------------------
+@REM Maven Start Up Batch script
+@REM
+@REM Required ENV vars:
+@REM JAVA_HOME - location of a JDK home dir
+@REM
+@REM Optional ENV vars
+@REM M2_HOME - location of maven2's installed home dir
+@REM MAVEN_BATCH_ECHO - set to 'on' to enable the echoing of the batch commands
+@REM MAVEN_BATCH_PAUSE - set to 'on' to wait for a keystroke before ending
+@REM MAVEN_OPTS - parameters passed to the Java VM when running Maven
+@REM     e.g. to debug Maven itself, use
+@REM set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+@REM MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+@REM ----------------------------------------------------------------------------
+
+@REM Begin all REM lines with '@' in case MAVEN_BATCH_ECHO is 'on'
+@echo off
+@REM set title of command window
+title %0
+@REM enable echoing by setting MAVEN_BATCH_ECHO to 'on'
+@if "%MAVEN_BATCH_ECHO%" == "on"  echo %MAVEN_BATCH_ECHO%
+
+@REM set %HOME% to equivalent of $HOME
+if "%HOME%" == "" (set "HOME=%HOMEDRIVE%%HOMEPATH%")
+
+@REM Execute a user defined script before this one
+if not "%MAVEN_SKIP_RC%" == "" goto skipRcPre
+@REM check for pre script, once with legacy .bat ending and once with .cmd ending
+if exist "%HOME%\mavenrc_pre.bat" call "%HOME%\mavenrc_pre.bat"
+if exist "%HOME%\mavenrc_pre.cmd" call "%HOME%\mavenrc_pre.cmd"
+:skipRcPre
+
+@setlocal
+
+set ERROR_CODE=0
+
+@REM To isolate internal variables from possible post scripts, we use another setlocal
+@setlocal
+
+@REM ==== START VALIDATION ====
+if not "%JAVA_HOME%" == "" goto OkJHome
+
+echo.
+echo Error: JAVA_HOME not found in your environment. >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+:OkJHome
+if exist "%JAVA_HOME%\bin\java.exe" goto init
+
+echo.
+echo Error: JAVA_HOME is set to an invalid directory. >&2
+echo JAVA_HOME = "%JAVA_HOME%" >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+@REM ==== END VALIDATION ====
+
+:init
+
+@REM Find the project base dir, i.e. the directory that contains the folder ".mvn".
+@REM Fallback to current working directory if not found.
+
+set MAVEN_PROJECTBASEDIR=%MAVEN_BASEDIR%
+IF NOT "%MAVEN_PROJECTBASEDIR%"=="" goto endDetectBaseDir
+
+set EXEC_DIR=%CD%
+set WDIR=%EXEC_DIR%
+:findBaseDir
+IF EXIST "%WDIR%"\.mvn goto baseDirFound
+cd ..
+IF "%WDIR%"=="%CD%" goto baseDirNotFound
+set WDIR=%CD%
+goto findBaseDir
+
+:baseDirFound
+set MAVEN_PROJECTBASEDIR=%WDIR%
+cd "%EXEC_DIR%"
+goto endDetectBaseDir
+
+:baseDirNotFound
+set MAVEN_PROJECTBASEDIR=%EXEC_DIR%
+cd "%EXEC_DIR%"
+
+:endDetectBaseDir
+
+IF NOT EXIST "%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config" goto endReadAdditionalConfig
+
+@setlocal EnableExtensions EnableDelayedExpansion
+for /F "usebackq delims=" %%a in ("%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config") do set JVM_CONFIG_MAVEN_PROPS=!JVM_CONFIG_MAVEN_PROPS! %%a
+@endlocal & set JVM_CONFIG_MAVEN_PROPS=%JVM_CONFIG_MAVEN_PROPS%
+
+:endReadAdditionalConfig
+
+SET MAVEN_JAVA_EXE="%JAVA_HOME%\bin\java.exe"
+set WRAPPER_JAR="%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.jar"
+set WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+set DOWNLOAD_URL="https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+
+FOR /F "tokens=1,2 delims==" %%A IN ("%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.properties") DO (
+    IF "%%A"=="wrapperUrl" SET DOWNLOAD_URL=%%B
+)
+
+@REM Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+@REM This allows using the maven wrapper in projects that prohibit checking in binary data.
+if exist %WRAPPER_JAR% (
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Found %WRAPPER_JAR%
+    )
+) else (
+    if not "%MVNW_REPOURL%" == "" (
+        SET DOWNLOAD_URL="%MVNW_REPOURL%/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    )
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Couldn't find %WRAPPER_JAR%, downloading it ...
+        echo Downloading from: %DOWNLOAD_URL%
+    )
+
+    powershell -Command "&{"^
+		"$webclient = new-object System.Net.WebClient;"^
+		"if (-not ([string]::IsNullOrEmpty('%MVNW_USERNAME%') -and [string]::IsNullOrEmpty('%MVNW_PASSWORD%'))) {"^
+		"$webclient.Credentials = new-object System.Net.NetworkCredential('%MVNW_USERNAME%', '%MVNW_PASSWORD%');"^
+		"}"^
+		"[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $webclient.DownloadFile('%DOWNLOAD_URL%', '%WRAPPER_JAR%')"^
+		"}"
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Finished downloading %WRAPPER_JAR%
+    )
+)
+@REM End of extension
+
+@REM Provide a "standardized" way to retrieve the CLI args that will
+@REM work with both Windows and non-Windows executions.
+set MAVEN_CMD_LINE_ARGS=%*
+
+%MAVEN_JAVA_EXE% %JVM_CONFIG_MAVEN_PROPS% %MAVEN_OPTS% %MAVEN_DEBUG_OPTS% -classpath %WRAPPER_JAR% "-Dmaven.multiModuleProjectDirectory=%MAVEN_PROJECTBASEDIR%" %WRAPPER_LAUNCHER% %MAVEN_CONFIG% %*
+if ERRORLEVEL 1 goto error
+goto end
+
+:error
+set ERROR_CODE=1
+
+:end
+@endlocal & set ERROR_CODE=%ERROR_CODE%
+
+if not "%MAVEN_SKIP_RC%" == "" goto skipRcPost
+@REM check for post script, once with legacy .bat ending and once with .cmd ending
+if exist "%HOME%\mavenrc_post.bat" call "%HOME%\mavenrc_post.bat"
+if exist "%HOME%\mavenrc_post.cmd" call "%HOME%\mavenrc_post.cmd"
+:skipRcPost
+
+@REM pause the script if MAVEN_BATCH_PAUSE is set to 'on'
+if "%MAVEN_BATCH_PAUSE%" == "on" pause
+
+if "%MAVEN_TERMINATE_CMD%" == "on" exit %ERROR_CODE%
+
+exit /B %ERROR_CODE%

docker/docker-spring-boot/pom.xml

@@ -0,0 +1,54 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>org.springframework.boot</groupId>
+        <artifactId>spring-boot-starter-parent</artifactId>
+        <version>2.3.1.RELEASE</version>
+        <relativePath/> <!-- lookup parent from repository -->
+    </parent>
+    <groupId>com.baeldung.docker</groupId>
+    <artifactId>spring-boot-docker</artifactId>
+    <version>0.0.1-SNAPSHOT</version>
+    <name>spring-boot-docker</name>
+    <description>Demo project showing Spring Boot and Docker</description>
+
+    <properties>
+        <java.version>8</java.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-web</artifactId>
+        </dependency>
+
+        <dependency>
+            <groupId>org.springframework.boot</groupId>
+            <artifactId>spring-boot-starter-test</artifactId>
+            <scope>test</scope>
+            <exclusions>
+                <exclusion>
+                    <groupId>org.junit.vintage</groupId>
+                    <artifactId>junit-vintage-engine</artifactId>
+                </exclusion>
+            </exclusions>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.springframework.boot</groupId>
+                <artifactId>spring-boot-maven-plugin</artifactId>
+                <configuration>
+                    <layers>
+                        <enabled>true</enabled>
+                    </layers>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

docker/docker-spring-boot/src/main/docker/Dockerfile

@@ -0,0 +1,15 @@
+# To build, run the following command from the top level project directory:
+#
+# docker build -f src/main/docker/Dockerfile .
+
+FROM adoptopenjdk:11-jre-hotspot as builder
+ARG JAR_FILE=target/*.jar
+COPY ${JAR_FILE} application.jar
+RUN java -Djarmode=layertools -jar application.jar extract
+
+FROM adoptopenjdk:11-jre-hotspot
+COPY --from=builder dependencies/ ./
+COPY --from=builder snapshot-dependencies/ ./
+COPY --from=builder spring-boot-loader/ ./
+COPY --from=builder application/ ./
+ENTRYPOINT ["java", "org.springframework.boot.loader.JarLauncher"]

docker/docker-spring-boot/src/main/java/com/baeldung/docker/DemoApplication.java

@@ -1,14 +1,13 @@
-package com.baeldung.multipledb;
+package com.baeldung.docker;
 
 import org.springframework.boot.SpringApplication;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 
 @SpringBootApplication
-public class MultipleDbApplication {
+public class DemoApplication {
 
     public static void main(String[] args) {
-        SpringApplication.run(MultipleDbApplication.class, args);
+        SpringApplication.run(DemoApplication.class, args);
     }
-    
-}
 
+}

docker/docker-spring-boot/src/main/java/com/baeldung/docker/HelloController.java

@@ -0,0 +1,16 @@
+package com.baeldung.docker;
+
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+public class HelloController {
+
+    @GetMapping("/hello")
+    public ResponseEntity<String> hello()
+    {
+        return ResponseEntity.ok("hello2    ");
+    }
+
+}

docker/docker-spring-boot/src/main/resources/application.properties

@@ -0,0 +1 @@
+

excelformula/README.md

@@ -0,0 +1,5 @@
+## Apache POI
+
+This module contains articles about Apache POI
+
+### Relevant Articles:

guava-2/README.md

@@ -1,7 +0,0 @@
-## Guava
-
-This module contains articles a Google Guava
-
-### Relevant Articles: 
-
-- [Guava CharMatcher](https://www.baeldung.com/guava-string-charmatcher)

guava-modules/guava-18/README.md

@@ -1,8 +1,5 @@
-=========
+## Guava 18
-
-## Guava and Hamcrest Cookbooks and Examples
 
 
 ### Relevant Articles: 
-- [Guava Functional Cookbook](http://www.baeldung.com/guava-functions-predicates)
 - [Guava 18: What’s New?](http://www.baeldung.com/whats-new-in-guava-18)

guava-modules/guava-19/README.md

@@ -1,5 +1,3 @@
-=========
-
 ## Guava 19
 
 

guava-modules/guava-21/README.md

@@ -1,4 +1,6 @@
+## Guava 21
+
 ### Relevant articles:
+
 - [New Stream, Comparator and Collector in Guava 21](http://www.baeldung.com/guava-21-new)
 - [New in Guava 21 common.util.concurrent](http://www.baeldung.com/guava-21-util-concurrent)
-- [Zipping Collections in Java](http://www.baeldung.com/java-collections-zip)

guava-modules/guava-21/pom.xml

@@ -13,17 +13,8 @@
         <relativePath>../</relativePath>
     </parent>
 
-    <dependencies>
-        <dependency>
-            <groupId>org.jooq</groupId>
-            <artifactId>jool</artifactId>
-            <version>${jool.version}</version>
-        </dependency>
-    </dependencies>
-
     <properties>
         <guava.version>21.0</guava.version>
-        <jool.version>0.9.12</jool.version>
     </properties>
 
 </project>

guava-modules/guava-collections-list/README.md

@@ -0,0 +1,8 @@
+## Guava Collections List examples
+
+This module contains articles about list collections in Guava
+
+### Relevant Articles: 
+
+- [Partition a List in Java](https://www.baeldung.com/java-list-split)
+- [Guava – Lists](https://www.baeldung.com/guava-lists)

guava-modules/guava-collections-list/pom.xml

@@ -4,15 +4,15 @@
     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
     <modelVersion>4.0.0</modelVersion>
-    <artifactId>guava-collections</artifactId>
+    <artifactId>guava-collections-list</artifactId>
     <version>0.1.0-SNAPSHOT</version>
-    <name>guava-collections</name>
+    <name>guava-collections-list</name>
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>guava-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>

guava-modules/guava-collections-map/pom.xml

@@ -9,9 +9,9 @@
 
     <parent>
         <groupId>com.baeldung</groupId>
-        <artifactId>parent-java</artifactId>
+        <artifactId>guava-modules</artifactId>
         <version>0.0.1-SNAPSHOT</version>
-        <relativePath>../parent-java</relativePath>
+        <relativePath>../</relativePath>
     </parent>
 
     <dependencies>