BAEL-1725 Java Pass-by-reference vs Pass-by-value - First commit (#4058)

* BAEL-1725 Java Pass-by-reference vs Pass-by-value - First commit

* updated test cases

core-java/src/main/java/com/baeldung/parameterpassing/NonPrimitives.java

@@ -0,0 +1,27 @@
+package com.baeldung.parameterpassing;
+
+public class NonPrimitives {
+    public static void main(String[] args) {
+        FooClass a = new FooClass(1);
+        FooClass b = new FooClass(1);
+ 
+        System.out.printf("Before Modification: a = %d and b = %d ", a.num, b.num);
+        modify(a, b);
+        System.out.printf("\nAfter Modification: a = %d and b = %d ", a.num, b.num);
+    }
+ 
+    public static void modify(FooClass a1, FooClass b1) {
+        a1.num++;
+       
+        b1 = new FooClass(1);
+        b1.num++;
+    }
+}
+ 
+class FooClass {
+    public int num;
+   
+    public FooClass(int num) {
+        this.num = num;
+    }
+}

core-java/src/main/java/com/baeldung/parameterpassing/Primitives.java

@@ -0,0 +1,17 @@
+package com.baeldung.parameterpassing;
+
+public class Primitives {
+    public static void main(String[] args) {
+        int x = 1;
+        int y = 2;
+       
+        System.out.printf("Before Modification: x = %d and y = %d ", x, y);
+        modify(x, y);
+        System.out.printf("\nAfter Modification: x = %d and y = %d ", x, y);
+    }
+   
+    public static void modify(int x1, int y1) {
+        x1 = 5;
+        y1 = 10;
+    }
+}

core-java/src/test/java/com/baeldung/parameterpassing/NonPrimitivesUnitTest.java

@@ -0,0 +1,37 @@
+package com.baeldung.parameterpassing;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class NonPrimitivesUnitTest {
+    @Test
+    public void whenModifyingObjects_thenOriginalObjectChanged() {
+        Foo a = new Foo(1);
+        Foo b = new Foo(1);
+
+        // Before Modification
+        Assert.assertEquals(a.num, 1);
+        Assert.assertEquals(b.num, 1);
+        
+        modify(a, b);
+        
+        // After Modification
+        Assert.assertEquals(a.num, 2);
+        Assert.assertEquals(b.num, 1);
+    }
+ 
+    public static void modify(Foo a1, Foo b1) {
+        a1.num++;
+       
+        b1 = new Foo(1);
+        b1.num++;
+    }
+}
+ 
+class Foo {
+    public int num;
+   
+    public Foo(int num) {
+        this.num = num;
+    }
+}

core-java/src/test/java/com/baeldung/parameterpassing/PrimitivesUnitTest.java

@@ -0,0 +1,28 @@
+package com.baeldung.parameterpassing;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class PrimitivesUnitTest {
+    @Test
+    public void whenModifyingPrimitives_thenOriginalValuesNotModified() {
+        
+        int x = 1;
+        int y = 2;
+       
+        // Before Modification
+        Assert.assertEquals(x, 1);
+        Assert.assertEquals(y, 2);
+        
+        modify(x, y);
+        
+        // After Modification
+        Assert.assertEquals(x, 1);
+        Assert.assertEquals(y, 2);
+    }
+    
+    public static void modify(int x1, int y1) {
+        x1 = 5;
+        y1 = 10;
+    }
+}