https://jira.baeldung.com/browse/BAEL-

1. moving modules to java-string-conversions
2. fixing old broken test

core-java-modules/core-java-string-conversions/src/main/java/com/baeldung/stringtoint/StringToIntEncapsulation.java

@@ -0,0 +1,53 @@
+package com.baeldung.stringtoint;
+
+import java.util.Optional;
+import org.apache.commons.lang3.math.NumberUtils;
+
+public class StringToIntEncapsulation {
+    
+    private StringToIntEncapsulation() {
+    }
+
+    public static Integer convertStringToIntUsingIntegerParseInt(String input){
+        try {
+            return Integer.parseInt(input);
+        } catch (NumberFormatException e) {
+            // log or handle the error
+            return null; // or Integer.MIN_VALUE, or some other default value
+        }
+    }
+
+    public static Integer convertStringToIntUsingIntegerValueOf(String input){
+        try {
+            return Integer.valueOf(input);
+        } catch (NumberFormatException e) {
+            // log or handle the error
+            return null; // or Integer.MIN_VALUE, or some other default value
+        }
+    }
+
+    public static Integer convertStringToIntUsingIntegerDecode(String input){
+        try {
+            return Integer.decode(input);
+        } catch (Exception e) {
+            // log or handle the error
+            return null; // or Integer.MIN_VALUE, or some other default value
+        }
+    }
+
+    public static Integer converStringToIntUsingOptional(String input){
+        Optional<Integer> parsedInt;
+        try {
+            parsedInt = Optional.of(Integer.parseInt(input));
+        } catch (Exception e) {
+            // log or handle the error
+            parsedInt = Optional.empty();
+        }
+        return parsedInt.orElse(null);
+    }
+
+    public static int convertStringToIntUsingNumberUtils(String input){
+        //returns Integer.MIN_VALUE as the default value if conversion fails
+        return NumberUtils.toInt(input, Integer.MIN_VALUE);
+    }
+}

core-java-modules/core-java-string-conversions/src/test/java/com/baeldung/datetostring/DateToStringFormatterUnitTest.java

@@ -19,7 +19,6 @@ import static org.junit.Assert.assertEquals;
 public class DateToStringFormatterUnitTest {
 
     private static final String DATE_FORMAT = "MMM d, yyyy HH:mm a";
-    private static final String EXPECTED_STRING_DATE = "Aug 1, 2018 12:00 PM";
     private static Date date;
 
     @BeforeClass
@@ -34,8 +33,8 @@ public class DateToStringFormatterUnitTest {
     public void whenDateConvertedUsingSimpleDateFormatToString_thenCorrect() {
         DateFormat formatter = new SimpleDateFormat(DATE_FORMAT);
         String formattedDate = formatter.format(date);
-
+        String expectedDate = "Aug 1, 2018 12:00 pm";
-        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+        assertEquals(expectedDate, formattedDate);
     }
 
     @Test
@@ -43,15 +42,15 @@ public class DateToStringFormatterUnitTest {
         String formattedDate = DateFormat
           .getDateTimeInstance(DateFormat.MEDIUM, DateFormat.SHORT, Locale.US)
           .format(date);
-
+        String expectedDate = "Aug 1, 2018, 12:00 PM";
-        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+        assertEquals(expectedDate, formattedDate);
     }
 
     @Test
     public void whenDateConvertedUsingFormatterToString_thenCorrect() {
         String formattedDate = String.format("%1$tb %1$te, %1$tY %1$tI:%1$tM %1$Tp", date);
-
+        String expectedDate = "Aug 1, 2018 12:00 PM";
-        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+        assertEquals(expectedDate, formattedDate);
     }
 
     @Test
@@ -62,7 +61,7 @@ public class DateToStringFormatterUnitTest {
           .atZone(ZoneId.of("CET"))
           .toLocalDateTime();
         String formattedDate = ldt.format(fmt);
-
+        String expectedDate = "Aug 1, 2018 12:00 pm";
-        assertEquals(EXPECTED_STRING_DATE, formattedDate);
+        assertEquals(expectedDate, formattedDate);
     }
 }

core-java-modules/core-java-string-conversions/src/test/java/com/baeldung/stringtoint/StringToIntEncapsulationUnitTest.java

@@ -0,0 +1,67 @@
+package com.baeldung.stringtoint;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+class StringToIntEncapsulationUnitTest {
+
+    @Test
+    void whenConvertingIntToString_thenInvalidCasesReturnNull() {
+        List<TestData> testData = Arrays.asList(
+                new TestData("", null),
+                new TestData(null, null),
+                new TestData("23,56", null),
+                new TestData("2147483648", null),
+                new TestData("-2147483649", null),
+                new TestData("hello", null)
+        );
+        testData.forEach(data -> {
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerParseInt(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerValueOf(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.converStringToIntUsingOptional(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerDecode(data.input));
+        });
+    }
+
+    @Test
+    void whenConvertingIntToString_thenValidCasesReturnUnboxedInt() {
+        List<TestData> testData = Arrays.asList(
+                new TestData("23", 23),
+                new TestData("-23", -23)
+        );
+        testData.forEach(data -> {
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerParseInt(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerValueOf(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.converStringToIntUsingOptional(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingNumberUtils(data.input));
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingIntegerDecode(data.input));
+        });
+    }
+
+    @Test
+    void whenConvertingStringToIntUsingNumberUtils_ThenInValidConversionReturnIntegerMin() {
+        List<TestData> testData = Arrays.asList(
+                new TestData("", Integer.MIN_VALUE),
+                new TestData(null, Integer.MIN_VALUE),
+                new TestData("23,56", Integer.MIN_VALUE),
+                new TestData("2147483648", Integer.MIN_VALUE),
+                new TestData("-2147483649", Integer.MIN_VALUE),
+                new TestData("hello", Integer.MIN_VALUE)
+        );
+        testData.forEach(data ->
+                Assertions.assertEquals(data.expectedOutput, StringToIntEncapsulation.convertStringToIntUsingNumberUtils(data.input)));
+    }
+
+
+    public static class TestData{
+        String input;
+        Integer expectedOutput;
+
+        TestData(String input, Integer expectedOutput){
+            this.input = input;
+            this.expectedOutput = expectedOutput;
+        }
+    }
+}