Added code for Mutable vs Immutable objects in java

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/objectcopy/DeepCopyPerson.java

@@ -1,23 +0,0 @@
-package com.baeldung.objectcopy;
-
-import java.io.*;
-
-class DeepCopyPerson implements Serializable {
-
-    int age;
-
-    public DeepCopyPerson(int age) {
-        this.age = age;
-    }
-
-    public static DeepCopyPerson deepCopy(DeepCopyPerson person) throws IOException, ClassNotFoundException {
-        ByteArrayOutputStream bos = new ByteArrayOutputStream();
-        ObjectOutputStream out = new ObjectOutputStream(bos);
-        out.writeObject(person);
-
-        ByteArrayInputStream bis = new ByteArrayInputStream(bos.toByteArray());
-        ObjectInputStream in = new ObjectInputStream(bis);
-
-        return (DeepCopyPerson) in.readObject();
-    }
-}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/objectcopy/ShallowCopyPerson.java

@@ -1,10 +0,0 @@
-package com.baeldung.objectcopy;
-
-class ShallowCopyPerson {
-
-    int age;
-
-    public ShallowCopyPerson(int age) {
-        this.age = age;
-    }
-}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/objectmutability/ImmutablePerson.java

@@ -0,0 +1,21 @@
+package com.baeldung.objectmutability;
+
+public final class ImmutablePerson {
+
+    private final String name;
+    private final int age;
+
+    public ImmutablePerson(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+}
+

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/objectcopy/DeepCopyPersonUnitTest.java

@@ -1,19 +0,0 @@
-package com.baeldung.objectcopy;
-
-import org.junit.jupiter.api.Test;
-
-import java.io.IOException;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
-public class DeepCopyPersonUnitTest {
-
-    @Test
-    public void givenPerson_whenDeepCopy_thenIndependentCopy() throws IOException, ClassNotFoundException {
-        DeepCopyPerson person1 = new DeepCopyPerson(30);
-        DeepCopyPerson person2 = DeepCopyPerson.deepCopy(person1);
-        person1.age = 25;
-
-        assertEquals(30, person2.age);
-    }
-}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/objectcopy/ShallowCopyPersonUnitTest.java

@@ -1,17 +0,0 @@
-package com.baeldung.objectcopy;
-
-import org.junit.jupiter.api.Test;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-
-public class ShallowCopyPersonUnitTest {
-
-    @Test
-    public void givenPerson_whenShallowCopy_thenSharedReference() {
-        ShallowCopyPerson person1 = new ShallowCopyPerson(30);
-        ShallowCopyPerson person2 = person1;
-        person1.age = 25;
-
-        assertEquals(25, person2.age);
-    }
-}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/objectmutability/ImmutableObjectExamplesUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.objectmutability;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotSame;
+
+public class ImmutableObjectExamplesUnitTest {
+
+    @Test
+    public void givenImmutableString_whenConcat_thenNotSameAndCorrectValues() {
+        String originalString = "Hello";
+        String modifiedString = originalString.concat(" World");
+
+        assertNotSame(originalString, modifiedString);
+
+        assertEquals("Hello", originalString);
+        assertEquals("Hello World", modifiedString);
+    }
+
+    @Test
+    public void givenImmutableInteger_whenAdd_thenNotSameAndCorrectValue() {
+        Integer immutableInt = 42;
+        Integer modifiedInt = immutableInt + 8;
+
+        assertNotSame(immutableInt, modifiedInt);
+
+        assertEquals(42, (int) immutableInt);
+        assertEquals(50, (int) modifiedInt);
+    }
+}
+
+

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/objectmutability/ImmutablePersonUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.objectmutability;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class ImmutablePersonUnitTest {
+
+    @Test
+    public void givenImmutablePerson_whenModifyName_thenCompilationError() {
+        ImmutablePerson person = new ImmutablePerson("John", 30);
+        // person.setName("Jane");
+    }
+
+    @Test
+    public void givenImmutablePerson_whenAccessFields_thenCorrectValues() {
+        ImmutablePerson person = new ImmutablePerson("John", 30);
+
+        assertEquals("John", person.getName());
+        assertEquals(30, person.getAge());
+    }
+}
+

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/objectmutability/MutableObjectExamplesUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.objectmutability;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class MutableObjectExamplesUnitTest {
+
+    @Test
+    public void givenMutableString_whenModify_thenCorrectValue() {
+        StringBuilder mutableString = new StringBuilder("Hello");
+        mutableString.append(" World");
+
+        assertEquals("Hello World", mutableString.toString());
+    }
+
+    @Test
+    public void givenMutableList_whenAddElement_thenCorrectSize() {
+        List<String> mutableList = new ArrayList<>();
+        mutableList.add("Java");
+
+        assertEquals(1, mutableList.size());
+    }
+}
+