This commit is contained in:
Jonathan Cook 2020-07-27 15:57:17 +02:00
commit cb9e336bd6
457 changed files with 22516 additions and 520 deletions

View File

@ -7,4 +7,6 @@
- [Efficiently Merge Sorted Java Sequences](https://www.baeldung.com/java-merge-sorted-sequences)
- [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)

View File

@ -0,0 +1,26 @@
package com.baeldung.algorithms.topkelements;
import java.util.ArrayList;
import java.util.List;
public class BruteForceTopKElementsFinder implements TopKElementsFinder<Integer> {
public List<Integer> findTopK(List<Integer> input, int k) {
List<Integer> array = new ArrayList<>(input);
List<Integer> topKList = new ArrayList<>();
for (int i = 0; i < k; i++) {
int maxIndex = 0;
for (int j = 1; j < array.size(); j++) {
if (array.get(j) > array.get(maxIndex)) {
maxIndex = j;
}
}
topKList.add(array.remove(maxIndex));
}
return topKList;
}
}

View File

@ -0,0 +1,26 @@
package com.baeldung.algorithms.topkelements;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.PriorityQueue;
public class MaxHeapTopKElementsFinder implements TopKElementsFinder<Integer> {
public List<Integer> findTopK(List<Integer> input, int k) {
PriorityQueue<Integer> maxHeap = new PriorityQueue<>();
input.forEach(number -> {
maxHeap.add(number);
if (maxHeap.size() > k) {
maxHeap.poll();
}
});
List<Integer> topKList = new ArrayList<>(maxHeap);
Collections.reverse(topKList);
return topKList;
}
}

View File

@ -0,0 +1,7 @@
package com.baeldung.algorithms.topkelements;
import java.util.List;
public interface TopKElementsFinder<T extends Comparable<T>> {
List<T> findTopK(List<T> input, int k);
}

View File

@ -0,0 +1,17 @@
package com.baeldung.algorithms.topkelements;
import java.util.Comparator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;
import java.util.stream.Collectors;
public class TreeSetTopKElementsFinder implements TopKElementsFinder<Integer> {
public List<Integer> findTopK(List<Integer> input, int k) {
Set<Integer> sortedSet = new TreeSet<>(Comparator.reverseOrder());
sortedSet.addAll(input);
return sortedSet.stream().limit(k).collect(Collectors.toList());
}
}

View File

@ -0,0 +1,46 @@
package com.baeldung.algorithms.topkelements;
import org.junit.Test;
import java.util.Arrays;
import java.util.List;
import static org.assertj.core.api.Java6Assertions.assertThat;
public class TopKElementsFinderUnitTest {
private final TopKElementsFinder<Integer> bruteForceFinder = new BruteForceTopKElementsFinder();
private final TopKElementsFinder<Integer> maxHeapFinder = new MaxHeapTopKElementsFinder();
private final TopKElementsFinder<Integer> treeSetFinder = new TreeSetTopKElementsFinder();
private final int k = 4;
private final List<Integer> distinctIntegers = Arrays.asList(1, 2, 3, 9, 7, 6, 12);
private final List<Integer> distinctIntegersTopK = Arrays.asList(9, 7, 6, 12);
private final List<Integer> nonDistinctIntegers = Arrays.asList(1, 2, 3, 3, 9, 9, 7, 6, 12);
private final List<Integer> nonDistinctIntegersTopK = Arrays.asList(9, 9, 7, 12);
@Test
public void givenArrayDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
assertThat(bruteForceFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
}
@Test
public void givenArrayDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
assertThat(maxHeapFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
}
@Test
public void givenArrayDistinctIntegers_whenTreeSetFindTopK_thenReturnKLargest() {
assertThat(treeSetFinder.findTopK(distinctIntegers, k)).containsOnlyElementsOf(distinctIntegersTopK);
}
@Test
public void givenArrayNonDistinctIntegers_whenBruteForceFindTopK_thenReturnKLargest() {
assertThat(bruteForceFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
}
@Test
public void givenArrayNonDistinctIntegers_whenMaxHeapFindTopK_thenReturnKLargest() {
assertThat(maxHeapFinder.findTopK(nonDistinctIntegers, k)).containsOnlyElementsOf(nonDistinctIntegersTopK);
}
}

View File

@ -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)

View File

@ -13,4 +13,5 @@ This module contains articles about core Groovy concepts
- [Converting a String to a Date in Groovy](https://www.baeldung.com/groovy-string-to-date)
- [Guide to I/O in Groovy](https://www.baeldung.com/groovy-io)
- [Convert String to Integer in Groovy](https://www.baeldung.com/groovy-convert-string-to-integer)
- [Groovy Variable Scope](https://www.baeldung.com/groovy/variable-scope)
- [[More -->]](/core-groovy-2)

View File

@ -8,7 +8,7 @@ This module contains articles about Java 11 core features
- [Java 11 Local Variable Syntax for Lambda Parameters](https://www.baeldung.com/java-var-lambda-params)
- [Java 11 String API Additions](https://www.baeldung.com/java-11-string-api)
- [Java 11 Nest Based Access Control](https://www.baeldung.com/java-nest-based-access-control)
- [Exploring the New HTTP Client in Java 9 and 11](https://www.baeldung.com/java-9-http-client)
- [Exploring the New HTTP Client in Java](https://www.baeldung.com/java-9-http-client)
- [An Introduction to Epsilon GC: A No-Op Experimental Garbage Collector](https://www.baeldung.com/jvm-epsilon-gc-garbage-collector)
- [Guide to jlink](https://www.baeldung.com/jlink)
- [Negate a Predicate Method Reference with Java 11](https://www.baeldung.com/java-negate-predicate-method-reference)

View File

@ -1,12 +1,15 @@
package com.baeldung.modules.main;
import com.baeldung.modules.hello.HelloInterface;
import com.baeldung.modules.hello.HelloModules;
import java.util.ServiceLoader;
public class MainApp {
public static void main(String[] args) {
HelloModules.doSomething();
HelloModules module = new HelloModules();
module.sayHello();
Iterable<HelloInterface> services = ServiceLoader.load(HelloInterface.class);
HelloInterface service = services.iterator().next();
service.sayHello();
}
}

View File

@ -13,3 +13,4 @@ This module contains articles about core Java features that have been introduced
- [Java 9 Platform Logging API](https://www.baeldung.com/java-9-logging-api)
- [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)

View File

@ -9,3 +9,4 @@ This module contains articles about Java 9 core features
- [Iterate Through a Range of Dates in Java](https://www.baeldung.com/java-iterate-date-range)
- [Initialize a HashMap in Java](https://www.baeldung.com/java-initialize-hashmap)
- [Immutable ArrayList in Java](https://www.baeldung.com/java-immutable-list)
- [Easy Ways to Write a Java InputStream to an OutputStream](https://www.baeldung.com/java-inputstream-to-outputstream)

View File

@ -5,4 +5,4 @@ This module contains complete guides about arrays in Java
### Relevant Articles:
- [Arrays in Java: A Reference Guide](https://www.baeldung.com/java-arrays-guide)
- [Guide to the java.util.Arrays Class](https://www.baeldung.com/java-util-arrays)
- [What is [Ljava.lang.Object;?]](https://www.baeldung.com/java-tostring-array)
- [What is \[Ljava.lang.Object;?](https://www.baeldung.com/java-tostring-array)

View File

@ -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)

View File

@ -15,4 +15,5 @@ This module contains articles about advanced topics about multithreading with co
- [The ABA Problem in Concurrency](https://www.baeldung.com/cs/aba-concurrency)
- [Introduction to Lock-Free Data Structures](https://www.baeldung.com/lock-free-programming)
- [Introduction to Exchanger in Java](https://www.baeldung.com/java-exchanger)
- [Why Not To Start A Thread In The Constructor?](https://www.baeldung.com/java-thread-constructor)
- [[<-- previous]](/core-java-modules/core-java-concurrency-advanced-2)

View File

@ -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)

View File

@ -1,3 +1,5 @@
### Relevant Articles:
- [Introduction to Lock Striping](https://www.baeldung.com/java-lock-stripping)
- [Guide to the Java TransferQueue](http://www.baeldung.com/java-transfer-queue)
- [[<-- Prev]](/core-java-modules/core-java-concurrency-collections)

View File

@ -3,9 +3,16 @@
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>
<groupId>com.baeldung.concurrent.lock</groupId>
<artifactId>core-java-concurrency-collections-2</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-concurrency-collections-2</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<dependencies>
<dependency>
@ -30,19 +37,6 @@
<scope>test</scope>
</dependency>
</dependencies>
<build>
<sourceDirectory>src</sourceDirectory>
<plugins>
<plugin>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<jmh.version>1.21</jmh.version>

View File

@ -19,7 +19,7 @@ import org.junit.FixMethodOrder;
import org.junit.Test;
@FixMethodOrder
public class TestConcurrentLinkedQueue {
public class ConcurrentLinkedQueueUnitTest {
@Test
public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {

View File

@ -18,7 +18,7 @@ import org.junit.FixMethodOrder;
import org.junit.Test;
@FixMethodOrder
public class TestLinkedBlockingQueue {
public class LinkedBlockingQueueUnitTest {
@Test
public void givenThereIsExistingCollection_WhenAddedIntoQueue_ThenShouldContainElements() {

View File

@ -4,7 +4,11 @@ import org.junit.FixMethodOrder;
import org.junit.Test;
import org.junit.runners.MethodSorters;
import java.util.concurrent.*;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedTransferQueue;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TransferQueue;
import static junit.framework.TestCase.assertEquals;

View File

@ -10,7 +10,7 @@ This module contains articles about concurrent Java collections
- [Custom Thread Pools In Java 8 Parallel Streams](http://www.baeldung.com/java-8-parallel-streams-custom-threadpool)
- [Guide to DelayQueue](http://www.baeldung.com/java-delay-queue)
- [A Guide to Java SynchronousQueue](http://www.baeldung.com/java-synchronous-queue)
- [Guide to the Java TransferQueue](http://www.baeldung.com/java-transfer-queue)
- [Guide to the ConcurrentSkipListMap](http://www.baeldung.com/java-concurrent-skip-list-map)
- [Guide to CopyOnWriteArrayList](http://www.baeldung.com/java-copy-on-write-arraylist)
- [LinkedBlockingQueue vs ConcurrentLinkedQueue](https://www.baeldung.com/java-queue-linkedblocking-concurrentlinked)
- [[Next -->]](/core-java-modules/core-java-concurrency-collections-2)

View File

@ -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);
}
}

View File

@ -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();
}
}

View File

@ -2,6 +2,7 @@
This module contains articles about date operations in Java.
### Relevant Articles:
- [Get the Current Date Prior to Java 8](https://www.baeldung.com/java-get-the-current-date-legacy)
- [Skipping Weekends While Adding Days to LocalDate in Java 8](https://www.baeldung.com/java-localdate-add-days-skip-weekends)
- [Checking If Two Java Dates Are on the Same Day](https://www.baeldung.com/java-check-two-dates-on-same-day)
@ -9,4 +10,5 @@ This module contains articles about date operations in Java.
- [How to Set the JVM Time Zone](https://www.baeldung.com/java-jvm-time-zone)
- [How to determine day of week by passing specific date in Java?](https://www.baeldung.com/java-get-day-of-week)
- [Finding Leap Years in Java](https://www.baeldung.com/java-leap-year)
- [Getting the Week Number From Any Date](https://www.baeldung.com/java-get-week-number)
- [[<-- Prev]](/core-java-modules/core-java-date-operations-1)

View File

@ -12,3 +12,5 @@ This module contains articles about core java exceptions
- [Java Try with Resources](https://www.baeldung.com/java-try-with-resources)
- [Java Global Exception Handler](https://www.baeldung.com/java-global-exception-handler)
- [How to Find an Exceptions 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)

View File

@ -13,4 +13,4 @@ This module contains articles about core Java input and output (IO)
- [How to Copy a File with Java](https://www.baeldung.com/java-copy-file)
- [Create a Directory in Java](https://www.baeldung.com/java-create-directory)
- [Java IO vs NIO](https://www.baeldung.com/java-io-vs-nio)
- [[<-- Prev]](/core-java-modules/core-java-io)
- [[<-- Prev]](/core-java-modules/core-java-io)[[More -->]](/core-java-modules/core-java-io-3)

View File

@ -0,0 +1,9 @@
## Core Java IO
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)

View File

@ -0,0 +1,59 @@
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-io-3</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-io-3</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<dependencies>
<!-- utils -->
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>${guava.version}</version>
</dependency>
<!-- utils -->
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>${commons-io.version}</version>
</dependency>
<!-- logging -->
<dependency>
<groupId>log4j</groupId>
<artifactId>log4j</artifactId>
<version>${log4j.version}</version>
</dependency>
<dependency> <!-- needed to bridge to slf4j for projects that use the log4j APIs directly -->
<groupId>org.slf4j</groupId>
<artifactId>log4j-over-slf4j</artifactId>
<version>${org.slf4j.version}</version>
</dependency>
<!-- test scoped -->
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
</build>
<properties>
<assertj.version>3.6.1</assertj.version>
</properties>
</project>

View File

@ -0,0 +1,50 @@
package com.baeldung.createfile;
import org.apache.commons.io.FileUtils;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.io.File;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import static org.junit.jupiter.api.Assertions.assertTrue;
public class CreateFileUnitTest {
private final String FILE_NAME = "src/test/resources/fileToCreate.txt";
@AfterEach
@BeforeEach
public void cleanUpFiles() {
File targetFile = new File(FILE_NAME);
targetFile.delete();
}
@Test
public void givenUsingNio_whenCreatingFile_thenCorrect() throws IOException {
Path newFilePath = Paths.get(FILE_NAME);
Files.createFile(newFilePath);
}
@Test
public void givenUsingFile_whenCreatingFile_thenCorrect() throws IOException {
File newFile = new File(FILE_NAME);
boolean success = newFile.createNewFile();
assertTrue(success);
}
@Test
public void givenUsingGuava_whenCreatingFile_thenCorrect() throws IOException {
com.google.common.io.Files.touch(new File(FILE_NAME));
}
@Test
public void givenUsingCommonsIo_whenCreatingFile_thenCorrect() throws IOException {
FileUtils.touch(new File(FILE_NAME));
}
}

View File

@ -0,0 +1,63 @@
package com.baeldung.emptiness;
import org.junit.Test;
import java.io.File;
import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.stream.Stream;
import static org.assertj.core.api.Assertions.assertThat;
public class DirectoryEmptinessUnitTest {
@Test
public void givenPath_whenInvalid_thenReturnsFalse() throws IOException {
assertThat(isEmpty(Paths.get("invalid-addr"))).isFalse();
}
@Test
public void givenPath_whenNotDirectory_thenReturnsFalse() throws IOException {
Path aFile = Paths.get(getClass().getResource("/notDir.txt").getPath());
assertThat(isEmpty(aFile)).isFalse();
}
@Test
public void givenPath_whenNotEmptyDir_thenReturnsFalse() throws IOException {
Path currentDir = new File("").toPath().toAbsolutePath();
assertThat(isEmpty(currentDir)).isFalse();
}
@Test
public void givenPath_whenIsEmpty_thenReturnsTrue() throws Exception {
Path path = Files.createTempDirectory("baeldung-empty");
assertThat(isEmpty(path)).isTrue();
}
private static boolean isEmpty(Path path) throws IOException {
if (Files.isDirectory(path)) {
try (DirectoryStream<Path> directory = Files.newDirectoryStream(path)) {
return !directory.iterator().hasNext();
}
}
return false;
}
private static boolean isEmpty2(Path path) throws IOException {
if (Files.isDirectory(path)) {
try (Stream<Path> entries = Files.list(path)) {
return !entries.findFirst().isPresent();
}
}
return false;
}
private static boolean isEmptyInefficient(Path path) {
return path.toFile().listFiles().length == 0;
}
}

View File

@ -7,7 +7,6 @@ This module contains articles about core Java input/output(IO) APIs.
- [A Guide to the Java FileReader Class](https://www.baeldung.com/java-filereader)
- [The Java File Class](https://www.baeldung.com/java-io-file)
- [Java FileWriter](https://www.baeldung.com/java-filewriter)
- [Differences Between the Java WatchService API and the Apache Commons IO Monitor Library](https://www.baeldung.com/java-watchservice-vs-apache-commons-io-monitor-library)
- [Comparing getPath(), getAbsolutePath(), and getCanonicalPath() in Java](https://www.baeldung.com/java-path)
- [Quick Use of FilenameFilter](https://www.baeldung.com/java-filename-filter)
- [Guide to BufferedReader](https://www.baeldung.com/java-buffered-reader)

View File

@ -6,4 +6,6 @@ This module contains articles about core Java input/output(IO) conversions.
- [Java InputStream to String](https://www.baeldung.com/convert-input-stream-to-string)
- [Java Write an InputStream to a File](https://www.baeldung.com/convert-input-stream-to-a-file)
- [Converting a BufferedReader to a JSONObject](https://www.baeldung.com/java-bufferedreader-to-jsonobject)
- [Reading a CSV File into an Array](https://www.baeldung.com/java-csv-file-array)
- [How to Write to a CSV File in Java](https://www.baeldung.com/java-csv)
- More articles: [[<-- prev]](/core-java-modules/core-java-io-conversions)

View File

@ -26,6 +26,12 @@
<artifactId>json</artifactId>
<version>${json.version}</version>
</dependency>
<dependency>
<groupId>com.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>${opencsv.version}</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
@ -40,6 +46,7 @@
<properties>
<json.version>20200518</json.version>
<opencsv.version>4.1</opencsv.version>
</properties>
</project>

View File

@ -1,20 +1,11 @@
package com.baeldung.csv;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
import com.opencsv.CSVReader;
import org.junit.Assert;
import org.junit.Test;
import com.opencsv.CSVReader;
import java.io.*;
import java.util.*;
public class ReadCSVInArrayUnitTest {
public static final String COMMA_DELIMITER = ",";

View File

@ -1,7 +1,9 @@
package com.baeldung.csv;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.io.File;
import java.io.FileNotFoundException;
@ -10,10 +12,8 @@ import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import org.junit.Before;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
public class WriteCsvFileExampleUnitTest {
private static final Logger LOG = LoggerFactory.getLogger(WriteCsvFileExampleUnitTest.class);

View File

@ -8,10 +8,9 @@ This module contains articles about core Java input and output (IO)
- [Java Directory Size](https://www.baeldung.com/java-folder-size)
- [File Size in Java](https://www.baeldung.com/java-file-size)
- [Zipping and Unzipping in Java](https://www.baeldung.com/java-compress-and-uncompress)
- [Reading a CSV File into an Array](https://www.baeldung.com/java-csv-file-array)
- [How to Get the File Extension of a File in Java](https://www.baeldung.com/java-file-extension)
- [Getting a Files Mime Type in Java](https://www.baeldung.com/java-file-mime-type)
- [How to Write to a CSV File in Java](https://www.baeldung.com/java-csv)
- [How to Avoid the Java FileNotFoundException When Loading Resources](https://www.baeldung.com/java-classpath-resource-cannot-be-opened)
- [Create a Directory in Java](https://www.baeldung.com/java-create-directory)
- [Java Rename or Move a File](https://www.baeldung.com/java-how-to-rename-or-move-a-file)
- [[More -->]](/core-java-modules/core-java-io-2)

View File

@ -29,12 +29,6 @@
<version>${hsqldb.version}</version>
<scope>runtime</scope>
</dependency>
<dependency>
<groupId>com.opencsv</groupId>
<artifactId>opencsv</artifactId>
<version>${opencsv.version}</version>
<scope>test</scope>
</dependency>
<!-- Mime Type Resolution Libraries -->
<dependency>
<groupId>org.apache.tika</groupId>
@ -142,8 +136,6 @@
</profiles>
<properties>
<!-- util -->
<opencsv.version>4.1</opencsv.version>
<!-- testing -->
<assertj.version>3.6.1</assertj.version>
<!-- maven plugins -->

View File

@ -0,0 +1,64 @@
package com.baeldung.rename;
import org.apache.commons.io.FileUtils;
import org.junit.jupiter.api.AfterEach;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;
import java.io.File;
import java.io.IOException;
import java.nio.file.FileSystemException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class RenameFileUnitTest {
private final String FILE_TO_MOVE = "src/test/resources/originalFileToMove.txt";
private final String TARGET_FILE = "src/test/resources/targetFileToMove.txt";
@BeforeEach
public void createFileToMove() throws IOException {
File fileToMove = new File(FILE_TO_MOVE);
fileToMove.createNewFile();
}
@AfterEach
public void cleanUpFiles() {
File targetFile = new File(TARGET_FILE);
targetFile.delete();
}
@Test
public void givenUsingNio_whenMovingFile_thenCorrect() throws IOException {
Path fileToMovePath = Paths.get(FILE_TO_MOVE);
Path targetPath = Paths.get(TARGET_FILE);
Files.move(fileToMovePath, targetPath);
}
@Test
public void givenUsingFileClass_whenMovingFile_thenCorrect() throws IOException {
File fileToMove = new File(FILE_TO_MOVE);
boolean isMoved = fileToMove.renameTo(new File(TARGET_FILE));
if (!isMoved) {
throw new FileSystemException(TARGET_FILE);
}
}
@Test
public void givenUsingGuava_whenMovingFile_thenCorrect()
throws IOException {
File fileToMove = new File(FILE_TO_MOVE);
File targetFile = new File(TARGET_FILE);
com.google.common.io.Files.move(fileToMove, targetFile);
}
@Test
public void givenUsingApache_whenMovingFile_thenCorrect() throws IOException {
FileUtils.moveFile(
FileUtils.getFile(FILE_TO_MOVE),
FileUtils.getFile(TARGET_FILE));
}
}

View File

@ -8,4 +8,6 @@ This module contains articles about working with the Java Virtual Machine (JVM).
- [Measuring Object Sizes in the JVM](https://www.baeldung.com/jvm-measuring-object-sizes)
- [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)

View File

@ -0,0 +1,24 @@
package com.baeldung.memaddress;
import org.junit.Test;
import org.openjdk.jol.vm.VM;
public class MemoryAddressUnitTest {
@Test
public void printTheMemoryAddress() {
String answer = "42";
System.out.println("The memory address is " + VM.current().addressOf(answer));
}
@Test
public void identityHashCodeAndMemoryAddress() {
Object obj = new Object();
System.out.println("Memory address: " + VM.current().addressOf(obj));
System.out.println("hashCode: " + obj.hashCode());
System.out.println("hashCode: " + System.identityHashCode(obj));
System.out.println("toString: " + obj);
}
}

View File

@ -2,4 +2,6 @@
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)

View File

@ -0,0 +1,23 @@
package com.baeldung.staticvariables;
public class StaticVariableDemo {
public static int i;
public static int j = 20;
public static int z;
static {
z = 30;
a = 40;
}
public static int a = 50;
public static final int b = 100;
public StaticVariableDemo() {
}
static class Nested {
public static String nestedClassStaticVariable = "test";
}
}

View File

@ -0,0 +1,113 @@
package com.baeldung.staticvariables;
import static org.assertj.core.api.Assertions.assertThat;
import java.lang.reflect.Field;
import org.junit.jupiter.api.Test;
public class StaticVariableUnitTest {
@Test
public void initializeStaticVariable_checkAssignedValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("i");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(0);
Field field2 = staticVariableDemo.getField("j");
assertThat(field2.getInt(staticVariableDemo)).isEqualTo(20);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkStaticBlock() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("z");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(30);
Field field2 = staticVariableDemo.getField("a");
assertThat(field2.getInt(staticVariableDemo)).isEqualTo(50);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkFinalValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Field field1 = staticVariableDemo.getField("b");
assertThat(field1.getInt(staticVariableDemo)).isEqualTo(100);
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
@Test
public void initializeStaticVariable_checkInnerClassValues() {
try {
Class<?> staticVariableDemo = this.getClass()
.getClassLoader()
.loadClass("com.baeldung.staticvariables.StaticVariableDemo");
Class<?>[] nestedClasses = staticVariableDemo.getClasses();
for (Class<?> nestedClass : nestedClasses) {
if (nestedClass.getName()
.equals("Nested")) {
Field field1 = nestedClass.getField("nestedClassStaticVariable");
assertThat(field1.get(nestedClass)).isEqualTo("test");
}
}
} catch (ClassNotFoundException | NoSuchFieldException | SecurityException e) {
e.printStackTrace();
} catch (IllegalArgumentException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
}
}
}

View File

@ -3,7 +3,9 @@
This module contains articles about methods in Java
### Relevant Articles:
- [Methods in Java](https://www.baeldung.com/java-methods)
- [Method Overloading and Overriding in Java](https://www.baeldung.com/java-method-overload-override)
- [Java equals() and hashCode() Contracts](https://www.baeldung.com/java-equals-hashcode-contracts)
- [Guide to hashCode() in Java](https://www.baeldung.com/java-hashcode)
- [The Covariant Return Type in Java](https://www.baeldung.com/java-covariant-return-type)

View File

@ -12,4 +12,5 @@ This module contains articles about networking in Java
- [Authentication with HttpUrlConnection](https://www.baeldung.com/java-http-url-connection)
- [Download a File from an URL in Java](https://www.baeldung.com/java-download-file)
- [Handling java.net.ConnectException](https://www.baeldung.com/java-net-connectexception)
- [Getting MAC addresses in Java](https://www.baeldung.com/java-mac-address)
- [[<-- Prev]](/core-java-modules/core-java-networking)

View File

@ -0,0 +1,3 @@
### Relevant Articles:
- [Reading the Value of private Fields from a Different Class in Java](https://www.baeldung.com/java-reflection-read-private-field-value)

View File

@ -8,5 +8,4 @@
- [Changing Annotation Parameters At Runtime](http://www.baeldung.com/java-reflection-change-annotation-params)
- [Dynamic Proxies in Java](http://www.baeldung.com/java-dynamic-proxies)
- [What Causes java.lang.reflect.InvocationTargetException?](https://www.baeldung.com/java-lang-reflect-invocationtargetexception)
- [How to Find all Getters Returning Null](http://www.baeldung.com/java-getters-returning-null)
- [How to Get a Name of a Method Being Executed?](http://www.baeldung.com/java-name-of-executing-method)

View File

@ -3,6 +3,7 @@
## Core Java 8 Cookbooks and Examples
### Relevant Articles:
- [An Overview of Regular Expressions Performance in Java](https://www.baeldung.com/java-regex-performance)
- [A Guide To Java Regular Expressions API](http://www.baeldung.com/regular-expressions-java)
- [Guide to Escaping Characters in Java RegExps](http://www.baeldung.com/java-regexp-escape-char)
@ -11,3 +12,4 @@
- [How to Use Regular Expressions to Replace Tokens in Strings](https://www.baeldung.com/java-regex-token-replacement)
- [Regular Expressions \s and \s+ in Java](https://www.baeldung.com/java-regex-s-splus)
- [Validate Phone Numbers With Java Regex](https://www.baeldung.com/java-regex-validate-phone-numbers)
- [How to Count the Number of Matches for a Regex?](https://www.baeldung.com/java-count-regex-matches)

View File

@ -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)

View File

@ -0,0 +1,3 @@
### Relevant Articles:
- [Version Comparison in Java](https://www.baeldung.com/java-comparing-versions)

View File

@ -0,0 +1,61 @@
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<artifactId>core-java-string-operations-3</artifactId>
<version>0.1.0-SNAPSHOT</version>
<name>core-java-string-operations-3</name>
<packaging>jar</packaging>
<parent>
<groupId>com.baeldung.core-java-modules</groupId>
<artifactId>core-java-modules</artifactId>
<version>0.0.1-SNAPSHOT</version>
<relativePath>../</relativePath>
</parent>
<dependencies>
<dependency>
<groupId>org.assertj</groupId>
<artifactId>assertj-core</artifactId>
<version>${assertj.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.apache.maven</groupId>
<artifactId>maven-artifact</artifactId>
<version>${maven-artifact.version}</version>
</dependency>
<dependency>
<groupId>org.gradle</groupId>
<artifactId>gradle-core</artifactId>
<version>${gradle-core.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.core</groupId>
<artifactId>jackson-core</artifactId>
<version>${jackson-core.version}</version>
</dependency>
<dependency>
<groupId>com.vdurmont</groupId>
<artifactId>semver4j</artifactId>
<version>${semver4j.version}</version>
</dependency>
</dependencies>
<properties>
<assertj.version>3.6.1</assertj.version>
<maven-artifact.version>3.6.3</maven-artifact.version>
<gradle-core.version>6.1.1</gradle-core.version>
<jackson-core.version>2.11.1</jackson-core.version>
<semver4j.version>3.1.0</semver4j.version>
</properties>
<repositories>
<repository>
<id>gradle-repo</id>
<url>https://repo.gradle.org/gradle/libs-releases-local/</url>
</repository>
</repositories>
</project>

View File

@ -0,0 +1,25 @@
package com.baeldung.versioncomparison;
public class VersionCompare {
public static int compareVersions(String version1, String version2) {
int comparisonResult = 0;
String[] version1Splits = version1.split("\\.");
String[] version2Splits = version2.split("\\.");
int maxLengthOfVersionSplits = Math.max(version1Splits.length, version2Splits.length);
for (int i = 0; i < maxLengthOfVersionSplits; i++){
Integer v1 = i < version1Splits.length ? Integer.parseInt(version1Splits[i]) : 0;
Integer v2 = i < version2Splits.length ? Integer.parseInt(version2Splits[i]) : 0;
int compare = v1.compareTo(v2);
if (compare != 0) {
comparisonResult = compare;
break;
}
}
return comparisonResult;
}
}

View File

@ -0,0 +1,136 @@
package com.baeldung.versioncomparison;
import org.junit.Test;
import com.fasterxml.jackson.core.Version;
import com.vdurmont.semver4j.Semver;
import com.vdurmont.semver4j.Semver.VersionDiff;
import org.apache.maven.artifact.versioning.ComparableVersion;
import org.gradle.util.VersionNumber;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertTrue;
public class VersionComparisonUnitTest {
@Test
public void givenVersionStrings_whenUsingMavenArtifact_thenCompareVersions() {
ComparableVersion version1_1 = new ComparableVersion("1.1");
ComparableVersion version1_2 = new ComparableVersion("1.2");
ComparableVersion version1_3 = new ComparableVersion("1.3");
assertTrue(version1_1.compareTo(version1_2) < 0);
assertTrue(version1_3.compareTo(version1_2) > 0);
ComparableVersion version1_1_0 = new ComparableVersion("1.1.0");
assertEquals(0, version1_1.compareTo(version1_1_0));
ComparableVersion version1_1_alpha = new ComparableVersion("1.1-alpha");
assertTrue(version1_1.compareTo(version1_1_alpha) > 0);
ComparableVersion version1_1_beta = new ComparableVersion("1.1-beta");
ComparableVersion version1_1_milestone = new ComparableVersion("1.1-milestone");
ComparableVersion version1_1_rc = new ComparableVersion("1.1-rc");
ComparableVersion version1_1_snapshot = new ComparableVersion("1.1-snapshot");
assertTrue(version1_1_alpha.compareTo(version1_1_beta) < 0);
assertTrue(version1_1_beta.compareTo(version1_1_milestone) < 0);
assertTrue(version1_1_rc.compareTo(version1_1_snapshot) < 0);
assertTrue(version1_1_snapshot.compareTo(version1_1) < 0);
ComparableVersion version1_1_c = new ComparableVersion("1.1-c");
ComparableVersion version1_1_z = new ComparableVersion("1.1-z");
ComparableVersion version1_1_1 = new ComparableVersion("1.1.1");
assertTrue(version1_1_c.compareTo(version1_1_z) < 0);
assertTrue(version1_1_z.compareTo(version1_1_1) < 0);
}
@Test
public void givenVersionStrings_whenUsingGradle_thenCompareVersions() {
VersionNumber version1_1 = VersionNumber.parse("1.1");
VersionNumber version1_2 = VersionNumber.parse("1.2");
VersionNumber version1_3 = VersionNumber.parse("1.3");
assertTrue(version1_1.compareTo(version1_2) < 0);
assertTrue(version1_3.compareTo(version1_2) > 0);
VersionNumber version1_1_0 = VersionNumber.parse("1.1.0");
assertEquals(0, version1_1.compareTo(version1_1_0));
VersionNumber version1_1_1_1_alpha = VersionNumber.parse("1.1.1.1-alpha");
assertTrue(version1_1.compareTo(version1_1_1_1_alpha) < 0);
VersionNumber version1_1_beta = VersionNumber.parse("1.1.0.0-beta");
assertTrue(version1_1_beta.compareTo(version1_1_1_1_alpha) < 0);
VersionNumber version1_1_1_snapshot = VersionNumber.parse("1.1.1-snapshot");
assertTrue(version1_1_1_1_alpha.compareTo(version1_1_1_snapshot) < 0);
}
@Test
public void givenVersionStrings_whenUsingJackson_thenCompareVersions() {
Version version1_1 = new Version(1, 1, 0, null, null, null);
Version version1_2 = new Version(1, 2, 0, null, null, null);
Version version1_3 = new Version(1, 3, 0, null, null, null);
assertTrue(version1_1.compareTo(version1_2) < 0);
assertTrue(version1_3.compareTo(version1_2) > 0);
Version version1_1_1 = new Version(1, 1, 1, null, null, null);
assertTrue(version1_1.compareTo(version1_1_1) < 0);
Version version1_1_maven = new Version(1, 1, 0, null, "org.apache.maven", null);
Version version1_1_gradle = new Version(1, 1, 0, null, "org.gradle", null);
assertTrue(version1_1_maven.compareTo(version1_1_gradle) < 0);
Version version1_1_snapshot = new Version(1, 1, 0, "snapshot", null, null);
assertEquals(0, version1_1.compareTo(version1_1_snapshot));
assertTrue(version1_1_snapshot.isSnapshot());
}
@Test
public void givenVersionStrings_whenUsingSemver_thenCompareVersions() {
Semver version1_1 = new Semver("1.1.0");
Semver version1_2 = new Semver("1.2.0");
Semver version1_3 = new Semver("1.3.0");
assertTrue(version1_1.compareTo(version1_2) < 0);
assertTrue(version1_3.compareTo(version1_2) > 0);
Semver version1_1_alpha = new Semver("1.1.0-alpha");
assertTrue(version1_1.isGreaterThan(version1_1_alpha));
Semver version1_1_beta = new Semver("1.1.0-beta");
Semver version1_1_milestone = new Semver("1.1.0-milestone");
Semver version1_1_rc = new Semver("1.1.0-rc");
Semver version1_1_snapshot = new Semver("1.1.0-snapshot");
assertTrue(version1_1_alpha.isLowerThan(version1_1_beta));
assertTrue(version1_1_beta.compareTo(version1_1_milestone) < 0);
assertTrue(version1_1_rc.compareTo(version1_1_snapshot) < 0);
assertTrue(version1_1_snapshot.compareTo(version1_1) < 0);
assertTrue(version1_1.isEqualTo("1.1.0"));
assertEquals(VersionDiff.MAJOR, version1_1.diff("2.1.0"));
assertEquals(VersionDiff.MINOR, version1_1.diff("1.2.3"));
assertEquals(VersionDiff.PATCH, version1_1.diff("1.1.1"));
assertTrue(version1_1.isStable());
assertFalse(version1_1_alpha.isStable());
}
@Test
public void givenVersionStrings_whenUsingCustomVersionCompare_thenCompareVersions() {
assertTrue(VersionCompare.compareVersions("1.0.1", "1.1.2") < 0);
assertTrue(VersionCompare.compareVersions("1.0.1", "1.10") < 0);
assertTrue(VersionCompare.compareVersions("1.1.2", "1.0.1") > 0);
assertTrue(VersionCompare.compareVersions("1.1.2", "1.2") < 0);
assertEquals(0, VersionCompare.compareVersions("1.3.0", "1.3"));
}
}

View File

@ -72,6 +72,7 @@
<module>core-java-io</module>
<module>core-java-io-2</module>
<module>core-java-io-3</module>
<module>core-java-io-apis</module>
<module>core-java-io-conversions</module>
<module>core-java-io-conversions-2</module>
@ -126,6 +127,7 @@
<module>core-java-string-conversions-2</module>
<module>core-java-string-operations</module>
<module>core-java-string-operations-2</module>
<module>core-java-string-operations-3</module>
<module>core-java-strings</module>
<module>core-java-sun</module>

View File

@ -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)

View File

@ -0,0 +1,33 @@
package com.baeldung.index
fun main() {
// Index only
val colors = listOf("Red", "Green", "Blue")
for (i in colors.indices) {
println(colors[i])
}
val colorArray = arrayOf("Red", "Green", "Blue")
for (i in colorArray.indices) {
println(colorArray[i])
}
(0 until colors.size).forEach { println(colors[it]) }
for (i in 0 until colors.size) {
println(colors[i])
}
// Index and Value
colors.forEachIndexed { i, v -> println("The value for index $i is $v") }
for (indexedValue in colors.withIndex()) {
println("The value for index ${indexedValue.index} is ${indexedValue.value}")
}
for ((i, v) in colors.withIndex()) {
println("The value for index $i is $v")
}
colors.filterIndexed { i, _ -> i % 2 == 0 }
colors.filterIndexed { _, v -> v == "RED" }
}

View File

@ -7,7 +7,6 @@ This module contains articles about core features in the Kotlin language.
- [Infix Functions in Kotlin](https://www.baeldung.com/kotlin-infix-functions)
- [Lambda Expressions in Kotlin](https://www.baeldung.com/kotlin-lambda-expressions)
- [Creating Java static final Equivalents in Kotlin](https://www.baeldung.com/kotlin-java-static-final)
- [Initializing Arrays in Kotlin](https://www.baeldung.com/kotlin-initialize-array)
- [Lazy Initialization in Kotlin](https://www.baeldung.com/kotlin-lazy-initialization)
- [Comprehensive Guide to Null Safety in Kotlin](https://www.baeldung.com/kotlin-null-safety)
- [Kotlin Scope Functions](https://www.baeldung.com/kotlin-scope-functions)

View File

@ -1,49 +0,0 @@
package com.baeldung.arrayinitialization
import org.junit.Test
import kotlin.test.assertEquals
class ArrayInitializationTest {
@Test
fun givenArrayOfStrings_thenValuesPopulated() {
val strings = arrayOf("January", "February", "March")
assertEquals(3, strings.size)
assertEquals("March", strings[2])
}
@Test
fun givenArrayOfIntegers_thenValuesPopulated() {
val integers = intArrayOf(1, 2, 3, 4)
assertEquals(4, integers.size)
assertEquals(1, integers[0])
}
@Test
fun givenArrayOfNulls_whenPopulated_thenValuesPresent() {
val array = arrayOfNulls<Number>(5)
for (i in array.indices) {
array[i] = i * i
}
assertEquals(16, array[4])
}
@Test
fun whenGeneratorUsed_thenValuesPresent() {
val generatedArray = IntArray(10) { i -> i * i }
assertEquals(81, generatedArray[9])
}
@Test
fun whenStringGenerated_thenValuesPresent() {
val generatedStringArray = Array(10) { i -> "Number of index: $i" }
assertEquals("Number of index: 0", generatedStringArray[0])
}
}

View File

@ -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)

View File

@ -0,0 +1,41 @@
package com.baeldung.anonymous
import java.io.Serializable
import java.nio.channels.Channel
fun main() {
val channel = object : Channel {
override fun isOpen() = false
override fun close() {
}
}
val maxEntries = 10
val lruCache = object : LinkedHashMap<String, Int>(10, 0.75f) {
override fun removeEldestEntry(eldest: MutableMap.MutableEntry<String, Int>?): Boolean {
return size > maxEntries
}
}
val map = object : LinkedHashMap<String, Int>() {
// omitted
}
val serializableChannel = object : Channel, Serializable {
override fun isOpen(): Boolean {
TODO("Not yet implemented")
}
override fun close() {
TODO("Not yet implemented")
}
}
val obj = object {
val question = "answer"
val answer = 42
}
println("The ${obj.question} is ${obj.answer}")
}

View File

@ -11,3 +11,4 @@ This module contains articles about data structures in Java
- [Introduction to Big Queue](https://www.baeldung.com/java-big-queue)
- [Guide to AVL Trees in Java](https://www.baeldung.com/java-avl-trees)
- [Graphs in Java](https://www.baeldung.com/java-graphs)
- [Implementing a Ring Buffer in Java](https://www.baeldung.com/java-ring-buffer)

View File

@ -0,0 +1,46 @@
package com.baeldung.ddd.order.config;
import org.bson.Document;
import org.joda.money.CurrencyUnit;
import org.joda.money.Money;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.convert.converter.Converter;
import org.springframework.data.convert.ReadingConverter;
import org.springframework.data.mongodb.core.convert.MongoCustomConversions;
import java.math.BigDecimal;
import java.util.Collections;
@Configuration
public class CustomMongoConfiguration {
@Bean
public MongoCustomConversions customConversions() {
return new MongoCustomConversions(Collections.singletonList(DocumentToMoneyConverter.INSTANCE));
}
@ReadingConverter
enum DocumentToMoneyConverter implements Converter<Document, Money> {
INSTANCE;
@Override
public Money convert(Document source) {
Document money = source.get("money", Document.class);
return Money.of(getCurrency(money), getAmount(money));
}
private CurrencyUnit getCurrency(Document money) {
Document currency = money.get("currency", Document.class);
String currencyCode = currency.getString("code");
return CurrencyUnit.of(currencyCode);
}
private BigDecimal getAmount(Document money) {
String amount = money.getString("amount");
return BigDecimal.valueOf(Double.parseDouble(amount));
}
}
}

View File

@ -1,19 +1,24 @@
package com.baeldung.ddd.order.jpa;
import static org.assertj.core.api.Assertions.assertThat;
import java.math.BigDecimal;
import java.util.Arrays;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
import java.math.BigDecimal;
import java.util.Arrays;
import static org.assertj.core.api.Assertions.assertThat;
/*
To run this test we need to run the databases first.
A dedicated docker-compose.yml file is located under the resources directory.
We can run it by simple executing `docker-compose up`.
*/
@SpringJUnitConfig
@SpringBootTest
public class PersistOrderIntegrationTest {
public class PersistOrderLiveTest {
@Autowired
private JpaOrderRepository repository;

View File

@ -17,9 +17,14 @@ import com.baeldung.ddd.order.Order;
import com.baeldung.ddd.order.OrderLine;
import com.baeldung.ddd.order.Product;
/*
To run this test we need to run the databases first.
A dedicated docker-compose.yml file is located under the resources directory.
We can run it by simple executing `docker-compose up`.
*/
@SpringJUnitConfig
@SpringBootTest
public class OrderMongoIntegrationTest {
public class OrderMongoLiveTest {
@Autowired
private OrderMongoRepository repo;

View File

@ -18,10 +18,15 @@ import com.baeldung.dddhexagonalspring.domain.Product;
import com.baeldung.dddhexagonalspring.domain.repository.OrderRepository;
import com.baeldung.dddhexagonalspring.infrastracture.repository.cassandra.SpringDataCassandraOrderRepository;
/*
To run this test we need to run the databases first.
A dedicated docker-compose.yml file is located under the resources directory.
We can run it by simple executing `docker-compose up`.
*/
@SpringJUnitConfig
@SpringBootTest
@TestPropertySource("classpath:ddd-layers-test.properties")
class CassandraDbOrderRepositoryIntegrationTest {
class CassandraDbOrderRepositoryLiveTest {
@Autowired
private SpringDataCassandraOrderRepository cassandraOrderRepository;

View File

@ -18,10 +18,15 @@ import com.baeldung.dddhexagonalspring.domain.Product;
import com.baeldung.dddhexagonalspring.domain.repository.OrderRepository;
import com.baeldung.dddhexagonalspring.infrastracture.repository.mongo.SpringDataMongoOrderRepository;
/*
To run this test we need to run the databases first.
A dedicated docker-compose.yml file is located under the resources directory.
We can run it by simple executing `docker-compose up`.
*/
@SpringJUnitConfig
@SpringBootTest
@TestPropertySource("classpath:ddd-layers-test.properties")
class MongoDbOrderRepositoryIntegrationTest {
class MongoDbOrderRepositoryLiveTest {
@Autowired
private SpringDataMongoOrderRepository mongoOrderRepository;

310
docker/docker-spring-boot/mvnw vendored Executable file
View File

@ -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} $MAVEN_CONFIG "$@"

182
docker/docker-spring-boot/mvnw.cmd vendored Normal file
View File

@ -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%

View File

@ -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>

View File

@ -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"]

View File

@ -0,0 +1,13 @@
package com.baeldung.docker;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class DemoApplication {
public static void main(String[] args) {
SpringApplication.run(DemoApplication.class, args);
}
}

View File

@ -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 ");
}
}

View File

@ -1,3 +1,4 @@
### Relevant Articles:
- [Run a Java main Method Using Gradle](https://www.baeldung.com/gradle-run-java-main)
- [Finding Unused Gradle Dependencies](https://www.baeldung.com/gradle-finding-unused-dependencies)

View File

@ -3,5 +3,5 @@
This module contains articles a Google Guava
### Relevant Articles:
- [Introduction to Guava Throwables](https://www.baeldung.com/guava-throwables)
- [Guava CharMatcher](https://www.baeldung.com/guava-string-charmatcher)

View File

@ -3,6 +3,7 @@
This module contains articles a Google Guava
### Relevant Articles:
- [Guava Functional Cookbook](https://www.baeldung.com/guava-functions-predicates)
- [Guide to Guavas PreConditions](https://www.baeldung.com/guava-preconditions)
- [Introduction to Guava CacheLoader](https://www.baeldung.com/guava-cacheloader)
@ -13,3 +14,4 @@ This module contains articles a Google Guava
- [Bloom Filter in Java using Guava](https://www.baeldung.com/guava-bloom-filter)
- [Quick Guide to the Guava RateLimiter](https://www.baeldung.com/guava-rate-limiter)
- [Guava Cache](https://www.baeldung.com/guava-cache)
- [Introduction to Guava Throwables](https://www.baeldung.com/guava-throwables)

View File

@ -6,3 +6,5 @@ This module contains articles about image processing.
- [Working with Images in Java](https://www.baeldung.com/java-images)
- [Intro to OpenCV with Java](https://www.baeldung.com/java-opencv)
- [Optical Character Recognition with Tesseract](https://www.baeldung.com/java-ocr-tesseract)
- [How Can I Resize an Image Using Java?](https://www.baeldung.com/java-resize-image)
- [Adding Text to an Image in Java](https://www.baeldung.com/java-add-text-to-image)

View File

@ -0,0 +1,70 @@
package com.baeldung.convertlisttomap;
import java.util.List;
import java.util.Map;
import java.util.function.BiConsumer;
import java.util.function.BinaryOperator;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Collectors;
/**
* Convert a string list to a map whose key is the string's length and value is the collection with same length.
* Give a list {"Baeldung", "is", "very", "cool"}.
* After conversion we'll get a map like:
* {8 : ["Baeldung"], 2 : ["is"], 4 : ["very", "cool"]}.
*
* @author leasy.zhang
*
*/
public class ListToMapConverter {
public Map<Integer, List<String>> groupingByStringLength(List<String> source,
Supplier<Map<Integer, List<String>>> mapSupplier,
Supplier<List<String>> listSupplier) {
return source.stream()
.collect(Collectors.groupingBy(String::length, mapSupplier, Collectors.toCollection(listSupplier)));
}
public Map<Integer, List<String>> streamCollectByStringLength(List<String> source,
Supplier<Map<Integer, List<String>>> mapSupplier,
Supplier<List<String>> listSupplier) {
BiConsumer<Map<Integer, List<String>>, String> accumulator = (response, element) -> {
Integer key = element.length();
List<String> values = response.getOrDefault(key, listSupplier.get());
values.add(element);
response.put(key, values);
};
BiConsumer<Map<Integer, List<String>>, Map<Integer, List<String>>> combiner = (res1, res2) -> {
res1.putAll(res2);
};
return source.stream()
.collect(mapSupplier, accumulator, combiner);
}
public Map<Integer, List<String>> collectorToMapByStringLength(List<String> source,
Supplier<Map<Integer, List<String>>> mapSupplier,
Supplier<List<String>> listSupplier) {
Function<String, Integer> keyMapper = String::length;
Function<String, List<String>> valueMapper = (element) -> {
List<String> collection = listSupplier.get();
collection.add(element);
return collection;
};
BinaryOperator<List<String>> mergeFunction = (existing, replacement) -> {
existing.addAll(replacement);
return existing;
};
return source.stream()
.collect(Collectors.toMap(keyMapper, valueMapper, mergeFunction, mapSupplier));
}
}

View File

@ -0,0 +1,46 @@
package com.baeldung.convertlisttomap;
import static org.junit.Assert.assertTrue;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.junit.Before;
import org.junit.Test;
public class ListToMapUnitTest {
private ListToMapConverter converter;
private List<String> source;
@Before
public void setUp() {
converter = new ListToMapConverter();
source = Arrays.asList("List", "Map", "Set", "Tree");
}
@Test
public void givenAList_whenConvertWithJava8GroupBy_thenReturnMap() {
Map<Integer, List<String>> convertedMap = converter.groupingByStringLength(source, HashMap::new, ArrayList::new);
assertTrue(convertedMap.get(3)
.contains("Map"));
}
@Test
public void givenAList_whenConvertWithJava8Collect_thenReturnMap() {
Map<Integer, List<String>> convertedMap = converter.streamCollectByStringLength(source, HashMap::new, ArrayList::new);
assertTrue(convertedMap.get(3)
.contains("Map"));
}
@Test
public void givenAList_whenConvertWithCollectorToMap_thenReturnMap() {
Map<Integer, List<String>> convertedMap = converter.collectorToMapByStringLength(source, HashMap::new, ArrayList::new);
assertTrue(convertedMap.get(3)
.contains("Map"));
}
}

View File

@ -11,4 +11,7 @@ This module contains articles about numbers in Java.
- [Listing Numbers Within a Range in Java](https://www.baeldung.com/java-listing-numbers-within-a-range)
- [Fibonacci Series in Java](https://www.baeldung.com/java-fibonacci)
- [Guide to the Number Class in Java](https://www.baeldung.com/java-number-class)
- [Print an Integer in Binary Format in Java](https://www.baeldung.com/java-print-integer-binary)
- [Number Formatting in Java](https://www.baeldung.com/java-number-formatting)
- [Division by Zero in Java: Exception, Infinity, or Not a Number](https://www.baeldung.com/java-division-by-zero)
- More articles: [[<-- prev]](/java-numbers-2)

View File

@ -5,4 +5,4 @@ This module contains articles about the Java Microbenchmark Harness (JMH).
### Relevant articles:
- [Microbenchmarking with Java](https://www.baeldung.com/java-microbenchmark-harness)
- [A Guide to False Sharing and @Contended](https://www.baeldung.com/java-false-sharing-contended)

View File

@ -0,0 +1,22 @@
package com.baeldung.falsesharing;
import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.Scope;
import org.openjdk.jmh.annotations.State;
@State(Scope.Benchmark)
public class FalseSharing {
private java.util.concurrent.atomic.LongAdder builtin = new java.util.concurrent.atomic.LongAdder();
private LongAdder custom = new LongAdder();
@Benchmark
public void builtin() {
builtin.increment();
}
@Benchmark
public void custom() {
custom.increment();
}
}

View File

@ -0,0 +1,237 @@
package com.baeldung.falsesharing;
import java.io.Serializable;
import java.util.concurrent.atomic.AtomicLong;
/**
* Copy-pasted from {@link java.util.concurrent.atomic.LongAdder}
*
* One or more variables that together maintain an initially zero
* {@code long} sum. When updates (method {@link #add}) are contended
* across threads, the set of variables may grow dynamically to reduce
* contention. Method {@link #sum} (or, equivalently, {@link
* #longValue}) returns the current total combined across the
* variables maintaining the sum.
*
* <p>This class is usually preferable to {@link AtomicLong} when
* multiple threads update a common sum that is used for purposes such
* as collecting statistics, not for fine-grained synchronization
* control. Under low update contention, the two classes have similar
* characteristics. But under high contention, expected throughput of
* this class is significantly higher, at the expense of higher space
* consumption.
*
* <p>LongAdders can be used with a {@link
* java.util.concurrent.ConcurrentHashMap} to maintain a scalable
* frequency map (a form of histogram or multiset). For example, to
* add a count to a {@code ConcurrentHashMap<String,LongAdder> freqs},
* initializing if not already present, you can use {@code
* freqs.computeIfAbsent(k -> new LongAdder()).increment();}
*
* <p>This class extends {@link Number}, but does <em>not</em> define
* methods such as {@code equals}, {@code hashCode} and {@code
* compareTo} because instances are expected to be mutated, and so are
* not useful as collection keys.
*
* @since 1.8
* @author Doug Lea
*/
public class LongAdder extends Striped64 implements Serializable {
private static final long serialVersionUID = 7249069246863182397L;
/**
* Creates a new adder with initial sum of zero.
*/
public LongAdder() {
}
/**
* Adds the given value.
*
* @param x the value to add
*/
public void add(long x) {
Cell[] as; long b, v; int m; Cell a;
if ((as = cells) != null || !casBase(b = base, b + x)) {
boolean uncontended = true;
if (as == null || (m = as.length - 1) < 0 ||
(a = as[getProbe() & m]) == null ||
!(uncontended = a.cas(v = a.value, v + x)))
longAccumulate(x, null, uncontended);
}
}
/**
* Equivalent to {@code add(1)}.
*/
public void increment() {
add(1L);
}
/**
* Equivalent to {@code add(-1)}.
*/
public void decrement() {
add(-1L);
}
/**
* Returns the current sum. The returned value is <em>NOT</em> an
* atomic snapshot; invocation in the absence of concurrent
* updates returns an accurate result, but concurrent updates that
* occur while the sum is being calculated might not be
* incorporated.
*
* @return the sum
*/
public long sum() {
Cell[] as = cells; Cell a;
long sum = base;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null)
sum += a.value;
}
}
return sum;
}
/**
* Resets variables maintaining the sum to zero. This method may
* be a useful alternative to creating a new adder, but is only
* effective if there are no concurrent updates. Because this
* method is intrinsically racy, it should only be used when it is
* known that no threads are concurrently updating.
*/
public void reset() {
Cell[] as = cells; Cell a;
base = 0L;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null)
a.value = 0L;
}
}
}
/**
* Equivalent in effect to {@link #sum} followed by {@link
* #reset}. This method may apply for example during quiescent
* points between multithreaded computations. If there are
* updates concurrent with this method, the returned value is
* <em>not</em> guaranteed to be the final value occurring before
* the reset.
*
* @return the sum
*/
public long sumThenReset() {
Cell[] as = cells; Cell a;
long sum = base;
base = 0L;
if (as != null) {
for (int i = 0; i < as.length; ++i) {
if ((a = as[i]) != null) {
sum += a.value;
a.value = 0L;
}
}
}
return sum;
}
/**
* Returns the String representation of the {@link #sum}.
* @return the String representation of the {@link #sum}
*/
public String toString() {
return Long.toString(sum());
}
/**
* Equivalent to {@link #sum}.
*
* @return the sum
*/
public long longValue() {
return sum();
}
/**
* Returns the {@link #sum} as an {@code int} after a narrowing
* primitive conversion.
*/
public int intValue() {
return (int)sum();
}
/**
* Returns the {@link #sum} as a {@code float}
* after a widening primitive conversion.
*/
public float floatValue() {
return (float)sum();
}
/**
* Returns the {@link #sum} as a {@code double} after a widening
* primitive conversion.
*/
public double doubleValue() {
return (double)sum();
}
/**
* Serialization proxy, used to avoid reference to the non-public
* Striped64 superclass in serialized forms.
* @serial include
*/
private static class SerializationProxy implements Serializable {
private static final long serialVersionUID = 7249069246863182397L;
/**
* The current value returned by sum().
* @serial
*/
private final long value;
SerializationProxy(LongAdder a) {
value = a.sum();
}
/**
* Return a {@code LongAdder} object with initial state
* held by this proxy.
*
* @return a {@code LongAdder} object with initial state
* held by this proxy.
*/
private Object readResolve() {
LongAdder a = new LongAdder();
a.base = value;
return a;
}
}
/**
* Returns a
* <a href="../../../../serialized-form.html#java.util.concurrent.atomic.LongAdder.SerializationProxy">
* SerializationProxy</a>
* representing the state of this instance.
*
* @return a {@link SerializationProxy}
* representing the state of this instance
*/
private Object writeReplace() {
return new SerializationProxy(this);
}
/**
* @param s the stream
* @throws java.io.InvalidObjectException always
*/
private void readObject(java.io.ObjectInputStream s)
throws java.io.InvalidObjectException {
throw new java.io.InvalidObjectException("Proxy required");
}
}

View File

@ -0,0 +1,395 @@
package com.baeldung.falsesharing;
import sun.misc.Unsafe;
import java.lang.reflect.Field;
import java.util.function.LongBinaryOperator;
import java.util.function.DoubleBinaryOperator;
import java.util.concurrent.ThreadLocalRandom;
/**
* Copy-pasted from {@code java.util.concurrent.atomic.Striped64} class.
*
* A package-local class holding common representation and mechanics
* for classes supporting dynamic striping on 64bit values. The class
* extends Number so that concrete subclasses must publicly do so.
*/
@SuppressWarnings("serial")
abstract class Striped64 extends Number {
/*
* This class maintains a lazily-initialized table of atomically
* updated variables, plus an extra "base" field. The table size
* is a power of two. Indexing uses masked per-thread hash codes.
* Nearly all declarations in this class are package-private,
* accessed directly by subclasses.
*
* Table entries are of class Cell; a variant of AtomicLong padded
* (via @sun.misc.Contended) to reduce cache contention. Padding
* is overkill for most Atomics because they are usually
* irregularly scattered in memory and thus don't interfere much
* with each other. But Atomic objects residing in arrays will
* tend to be placed adjacent to each other, and so will most
* often share cache lines (with a huge negative performance
* impact) without this precaution.
*
* In part because Cells are relatively large, we avoid creating
* them until they are needed. When there is no contention, all
* updates are made to the base field. Upon first contention (a
* failed CAS on base update), the table is initialized to size 2.
* The table size is doubled upon further contention until
* reaching the nearest power of two greater than or equal to the
* number of CPUS. Table slots remain empty (null) until they are
* needed.
*
* A single spinlock ("cellsBusy") is used for initializing and
* resizing the table, as well as populating slots with new Cells.
* There is no need for a blocking lock; when the lock is not
* available, threads try other slots (or the base). During these
* retries, there is increased contention and reduced locality,
* which is still better than alternatives.
*
* The Thread probe fields maintained via ThreadLocalRandom serve
* as per-thread hash codes. We let them remain uninitialized as
* zero (if they come in this way) until they contend at slot
* 0. They are then initialized to values that typically do not
* often conflict with others. Contention and/or table collisions
* are indicated by failed CASes when performing an update
* operation. Upon a collision, if the table size is less than
* the capacity, it is doubled in size unless some other thread
* holds the lock. If a hashed slot is empty, and lock is
* available, a new Cell is created. Otherwise, if the slot
* exists, a CAS is tried. Retries proceed by "double hashing",
* using a secondary hash (Marsaglia XorShift) to try to find a
* free slot.
*
* The table size is capped because, when there are more threads
* than CPUs, supposing that each thread were bound to a CPU,
* there would exist a perfect hash function mapping threads to
* slots that eliminates collisions. When we reach capacity, we
* search for this mapping by randomly varying the hash codes of
* colliding threads. Because search is random, and collisions
* only become known via CAS failures, convergence can be slow,
* and because threads are typically not bound to CPUS forever,
* may not occur at all. However, despite these limitations,
* observed contention rates are typically low in these cases.
*
* It is possible for a Cell to become unused when threads that
* once hashed to it terminate, as well as in the case where
* doubling the table causes no thread to hash to it under
* expanded mask. We do not try to detect or remove such cells,
* under the assumption that for long-running instances, observed
* contention levels will recur, so the cells will eventually be
* needed again; and for short-lived ones, it does not matter.
*/
/**
* Padded variant of AtomicLong supporting only raw accesses plus CAS.
*
* JVM intrinsics note: It would be possible to use a release-only
* form of CAS here, if it were provided.
*/
@sun.misc.Contended static final class Cell {
volatile long value;
Cell(long x) { value = x; }
final boolean cas(long cmp, long val) {
return UNSAFE.compareAndSwapLong(this, valueOffset, cmp, val);
}
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE;
private static final long valueOffset;
static {
try {
UNSAFE = getUnsafe();
Class<?> ak = Striped64.Cell.class;
valueOffset = UNSAFE.objectFieldOffset
(ak.getDeclaredField("value"));
} catch (Exception e) {
throw new Error(e);
}
}
}
/** Number of CPUS, to place bound on table size */
static final int NCPU = Runtime.getRuntime().availableProcessors();
/**
* Table of cells. When non-null, size is a power of 2.
*/
transient volatile Striped64.Cell[] cells;
/**
* Base value, used mainly when there is no contention, but also as
* a fallback during table initialization races. Updated via CAS.
*/
transient volatile long base;
/**
* Spinlock (locked via CAS) used when resizing and/or creating Cells.
*/
transient volatile int cellsBusy;
/**
* Package-private default constructor
*/
Striped64() {
}
/**
* CASes the base field.
*/
final boolean casBase(long cmp, long val) {
return UNSAFE.compareAndSwapLong(this, BASE, cmp, val);
}
/**
* CASes the cellsBusy field from 0 to 1 to acquire lock.
*/
final boolean casCellsBusy() {
return UNSAFE.compareAndSwapInt(this, CELLSBUSY, 0, 1);
}
/**
* Returns the probe value for the current thread.
* Duplicated from ThreadLocalRandom because of packaging restrictions.
*/
static final int getProbe() {
return UNSAFE.getInt(Thread.currentThread(), PROBE);
}
/**
* Pseudo-randomly advances and records the given probe value for the
* given thread.
* Duplicated from ThreadLocalRandom because of packaging restrictions.
*/
static final int advanceProbe(int probe) {
probe ^= probe << 13; // xorshift
probe ^= probe >>> 17;
probe ^= probe << 5;
UNSAFE.putInt(Thread.currentThread(), PROBE, probe);
return probe;
}
/**
* Handles cases of updates involving initialization, resizing,
* creating new Cells, and/or contention. See above for
* explanation. This method suffers the usual non-modularity
* problems of optimistic retry code, relying on rechecked sets of
* reads.
*
* @param x the value
* @param fn the update function, or null for add (this convention
* avoids the need for an extra field or function in LongAdder).
* @param wasUncontended false if CAS failed before call
*/
final void longAccumulate(long x, LongBinaryOperator fn,
boolean wasUncontended) {
int h;
if ((h = getProbe()) == 0) {
ThreadLocalRandom.current(); // force initialization
h = getProbe();
wasUncontended = true;
}
boolean collide = false; // True if last slot nonempty
for (;;) {
Striped64.Cell[] as; Striped64.Cell a; int n; long v;
if ((as = cells) != null && (n = as.length) > 0) {
if ((a = as[(n - 1) & h]) == null) {
if (cellsBusy == 0) { // Try to attach new Cell
Striped64.Cell r = new Striped64.Cell(x); // Optimistically create
if (cellsBusy == 0 && casCellsBusy()) {
boolean created = false;
try { // Recheck under lock
Striped64.Cell[] rs; int m, j;
if ((rs = cells) != null &&
(m = rs.length) > 0 &&
rs[j = (m - 1) & h] == null) {
rs[j] = r;
created = true;
}
} finally {
cellsBusy = 0;
}
if (created)
break;
continue; // Slot is now non-empty
}
}
collide = false;
}
else if (!wasUncontended) // CAS already known to fail
wasUncontended = true; // Continue after rehash
else if (a.cas(v = a.value, ((fn == null) ? v + x :
fn.applyAsLong(v, x))))
break;
else if (n >= NCPU || cells != as)
collide = false; // At max size or stale
else if (!collide)
collide = true;
else if (cellsBusy == 0 && casCellsBusy()) {
try {
if (cells == as) { // Expand table unless stale
Striped64.Cell[] rs = new Striped64.Cell[n << 1];
for (int i = 0; i < n; ++i)
rs[i] = as[i];
cells = rs;
}
} finally {
cellsBusy = 0;
}
collide = false;
continue; // Retry with expanded table
}
h = advanceProbe(h);
}
else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
boolean init = false;
try { // Initialize table
if (cells == as) {
Striped64.Cell[] rs = new Striped64.Cell[2];
rs[h & 1] = new Striped64.Cell(x);
cells = rs;
init = true;
}
} finally {
cellsBusy = 0;
}
if (init)
break;
}
else if (casBase(v = base, ((fn == null) ? v + x :
fn.applyAsLong(v, x))))
break; // Fall back on using base
}
}
/**
* Same as longAccumulate, but injecting long/double conversions
* in too many places to sensibly merge with long version, given
* the low-overhead requirements of this class. So must instead be
* maintained by copy/paste/adapt.
*/
final void doubleAccumulate(double x, DoubleBinaryOperator fn,
boolean wasUncontended) {
int h;
if ((h = getProbe()) == 0) {
ThreadLocalRandom.current(); // force initialization
h = getProbe();
wasUncontended = true;
}
boolean collide = false; // True if last slot nonempty
for (;;) {
Striped64.Cell[] as; Striped64.Cell a; int n; long v;
if ((as = cells) != null && (n = as.length) > 0) {
if ((a = as[(n - 1) & h]) == null) {
if (cellsBusy == 0) { // Try to attach new Cell
Striped64.Cell r = new Striped64.Cell(Double.doubleToRawLongBits(x));
if (cellsBusy == 0 && casCellsBusy()) {
boolean created = false;
try { // Recheck under lock
Striped64.Cell[] rs; int m, j;
if ((rs = cells) != null &&
(m = rs.length) > 0 &&
rs[j = (m - 1) & h] == null) {
rs[j] = r;
created = true;
}
} finally {
cellsBusy = 0;
}
if (created)
break;
continue; // Slot is now non-empty
}
}
collide = false;
}
else if (!wasUncontended) // CAS already known to fail
wasUncontended = true; // Continue after rehash
else if (a.cas(v = a.value,
((fn == null) ?
Double.doubleToRawLongBits
(Double.longBitsToDouble(v) + x) :
Double.doubleToRawLongBits
(fn.applyAsDouble
(Double.longBitsToDouble(v), x)))))
break;
else if (n >= NCPU || cells != as)
collide = false; // At max size or stale
else if (!collide)
collide = true;
else if (cellsBusy == 0 && casCellsBusy()) {
try {
if (cells == as) { // Expand table unless stale
Striped64.Cell[] rs = new Striped64.Cell[n << 1];
for (int i = 0; i < n; ++i)
rs[i] = as[i];
cells = rs;
}
} finally {
cellsBusy = 0;
}
collide = false;
continue; // Retry with expanded table
}
h = advanceProbe(h);
}
else if (cellsBusy == 0 && cells == as && casCellsBusy()) {
boolean init = false;
try { // Initialize table
if (cells == as) {
Striped64.Cell[] rs = new Striped64.Cell[2];
rs[h & 1] = new Striped64.Cell(Double.doubleToRawLongBits(x));
cells = rs;
init = true;
}
} finally {
cellsBusy = 0;
}
if (init)
break;
}
else if (casBase(v = base,
((fn == null) ?
Double.doubleToRawLongBits
(Double.longBitsToDouble(v) + x) :
Double.doubleToRawLongBits
(fn.applyAsDouble
(Double.longBitsToDouble(v), x)))))
break; // Fall back on using base
}
}
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE;
private static final long BASE;
private static final long CELLSBUSY;
private static final long PROBE;
static {
try {
UNSAFE = getUnsafe();
Class<?> sk = Striped64.class;
BASE = UNSAFE.objectFieldOffset
(sk.getDeclaredField("base"));
CELLSBUSY = UNSAFE.objectFieldOffset
(sk.getDeclaredField("cellsBusy"));
Class<?> tk = Thread.class;
PROBE = UNSAFE.objectFieldOffset
(tk.getDeclaredField("threadLocalRandomProbe"));
} catch (Exception e) {
throw new Error(e);
}
}
private static Unsafe getUnsafe() {
try {
Field field = Unsafe.class.getDeclaredField("theUnsafe");
field.setAccessible(true);
return (Unsafe) field.get(null);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}

View File

@ -15,4 +15,5 @@ Remember, for advanced libraries like [Jackson](/jackson) and [JUnit](/testing-m
- [A Guide to the Reflections Library](https://www.baeldung.com/reflections-library)
- [Exactly Once Processing in Kafka](https://www.baeldung.com/kafka-exactly-once)
- [Introduction to Protonpack](https://www.baeldung.com/java-protonpack)
- [Java-R Integration](https://www.baeldung.com/java-r-integration)
- More articles [[<-- prev]](/libraries-5)

View File

@ -92,8 +92,50 @@
<version>${commonsio.version}</version>
<scope>test</scope>
</dependency>
<dependency>
<groupId>org.rosuda.REngine</groupId>
<artifactId>Rserve</artifactId>
<version>${rserve.version}</version>
</dependency>
<dependency>
<groupId>com.github.jbytecode</groupId>
<artifactId>RCaller</artifactId>
<version>${rcaller.version}</version>
</dependency>
<dependency>
<groupId>org.renjin</groupId>
<artifactId>renjin-script-engine</artifactId>
<version>${renjin.version}</version>
</dependency>
</dependencies>
<repositories>
<!-- Needed for Renjin -->
<repository>
<id>bedatadriven</id>
<name>bedatadriven public repo</name>
<url>https://nexus.bedatadriven.com/content/groups/public/</url>
</repository>
</repositories>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<!-- Excludes FastR classes from compilations since they require GraalVM -->
<excludes>
<exclude>com/baeldung/r/FastRMean.java</exclude>
</excludes>
<testExcludes>
<exclude>com/baeldung/r/FastRMeanUnitTest.java</exclude>
</testExcludes>
</configuration>
</plugin>
</plugins>
</build>
<properties>
<kafka.version>2.0.0</kafka.version>
<javapoet.version>1.10.0</javapoet.version>
@ -105,6 +147,9 @@
<commons-net.version>3.6</commons-net.version>
<assertj.version>3.6.2</assertj.version>
<commonsio.version>2.6</commonsio.version>
<renjin.version>RELEASE</renjin.version>
<rcaller.version>3.0</rcaller.version>
<rserve.version>1.8.1</rserve.version>
</properties>

View File

@ -1,8 +1,5 @@
package com.baeldung.r;
import java.io.IOException;
import java.net.URISyntaxException;
/**
* FastR showcase.
*

View File

@ -1,12 +1,12 @@
package com.baeldung.r;
import java.io.IOException;
import java.net.URISyntaxException;
import com.github.rcaller.rstuff.RCaller;
import com.github.rcaller.rstuff.RCallerOptions;
import com.github.rcaller.rstuff.RCode;
import java.io.IOException;
import java.net.URISyntaxException;
/**
* RCaller showcase.
*

View File

@ -1,13 +1,12 @@
package com.baeldung.r;
import java.io.IOException;
import java.net.URISyntaxException;
import javax.script.ScriptException;
import org.renjin.script.RenjinScriptEngine;
import org.renjin.sexp.DoubleArrayVector;
import javax.script.ScriptException;
import java.io.IOException;
import java.net.URISyntaxException;
/**
* Renjin showcase.
*

View File

@ -1,14 +1,13 @@
package com.baeldung.r;
import java.io.IOException;
import java.net.URISyntaxException;
import javax.script.ScriptException;
import org.junit.Assert;
import org.junit.Ignore;
import org.junit.Test;
import javax.script.ScriptException;
import java.io.IOException;
import java.net.URISyntaxException;
/**
* Test for {@link RCallerMean}.
*

Some files were not shown because too many files have changed in this diff Show More