3-Third commit for articles:

* to core-java-lang:
  * https://www.baeldung.com/java-lang-system
  * https://www.baeldung.com/java-type-erasure
  * https://www.baeldung.com/java-assert
  * https://www.baeldung.com/java-pass-by-value-or-pass-by-reference
  * https://www.baeldung.com/java-variable-method-hiding
  * https://www.baeldung.com/java-access-modifiers
  * https://www.baeldung.com/java-super
  * https://www.baeldung.com/java-this
  * https://www.baeldung.com/java-immutable-object
  * https://www.baeldung.com/java-classnotfoundexception-and-noclassdeffounderror
  * https://www.baeldung.com/infinite-loops-java (changes for this were included in commit 1, with other loop-related examples)

core-java-lang/src/test/java/com/baeldung/classnotfoundexception/ClassNotFoundExceptionUnitTest.java

@@ -0,0 +1,11 @@
+package com.baeldung.classnotfoundexception;
+
+import org.junit.Test;
+
+public class ClassNotFoundExceptionUnitTest {
+
+    @Test(expected = ClassNotFoundException.class)
+    public void givenNoDriversInClassPath_whenLoadDrivers_thenClassNotFoundException() throws ClassNotFoundException {
+        Class.forName("oracle.jdbc.driver.OracleDriver");
+    }
+}

core-java-lang/src/test/java/com/baeldung/immutableobjects/ImmutableObjectsUnitTest.java

@@ -0,0 +1,36 @@
+package com.baeldung.immutableobjects;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.Test;
+
+public class ImmutableObjectsUnitTest {
+
+    @Test
+    public void whenCallingStringReplace_thenStringDoesNotMutate() {
+        // 2. What's an Immutable Object?
+        final String name = "baeldung";
+        final String newName = name.replace("dung", "----");
+
+        assertEquals("baeldung", name);
+        assertEquals("bael----", newName);
+    }
+
+    public void whenReassignFinalValue_thenCompilerError() {
+        // 3. The final Keyword in Java (1)
+        final String name = "baeldung";
+        // name = "bael...";
+    }
+
+    @Test
+    public void whenAddingElementToList_thenSizeChange() {
+        // 3. The final Keyword in Java (2)
+        final List<String> strings = new ArrayList<>();
+        assertEquals(0, strings.size());
+        strings.add("baeldung");
+        assertEquals(1, strings.size());
+    }
+}

core-java-lang/src/test/java/com/baeldung/noclassdeffounderror/NoClassDefFoundErrorUnitTest.java

@@ -0,0 +1,12 @@
+package com.baeldung.noclassdeffounderror;
+
+import org.junit.Test;
+
+public class NoClassDefFoundErrorUnitTest {
+
+    @Test(expected = NoClassDefFoundError.class)
+    public void givenInitErrorInClass_whenloadClass_thenNoClassDefFoundError() {
+        NoClassDefFoundErrorExample sample = new NoClassDefFoundErrorExample();
+        sample.getClassWithInitErrors();
+    }
+}

core-java-lang/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-lang/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;
+    }
+}

core-java-lang/src/test/java/com/baeldung/system/DateTimeServiceUnitTest.java

@@ -0,0 +1,15 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class DateTimeServiceUnitTest {
+
+    @Test
+    public void givenClass_whenCalledMethods_thenNotNullInResult() {
+        DateTimeService dateTimeService = new DateTimeService();
+
+        Assert.assertNotNull(dateTimeService.nowPlusOneHour());
+        Assert.assertNotNull(dateTimeService.nowPrettyPrinted());
+    }
+}

core-java-lang/src/test/java/com/baeldung/system/EnvironmentVariablesUnitTest.java

@@ -0,0 +1,14 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class EnvironmentVariablesUnitTest {
+
+    @Test
+    public void givenEnvVars_whenReadPath_thenGetValueinResult() {
+        EnvironmentVariables environmentVariables = new EnvironmentVariables();
+
+        Assert.assertNotNull(environmentVariables.getPath());
+    }
+}

core-java-lang/src/test/java/com/baeldung/system/SystemArrayCopyUnitTest.java

@@ -0,0 +1,27 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SystemArrayCopyUnitTest {
+
+    @Test
+    public void givenTwoArraysAB_whenUseArrayCopy_thenArrayCopiedFromAToBInResult() {
+        int[] a = {34, 22, 44, 2, 55, 3};
+        int[] b = new int[a.length];
+
+        // copy all elements from a to b
+        System.arraycopy(a, 0, b, 0, a.length);
+        Assert.assertArrayEquals(a, b);
+    }
+
+    @Test
+    public void givenTwoArraysAB_whenUseArrayCopyPosition_thenArrayCopiedFromAToBInResult() {
+        int[] a = {34, 22, 44, 2, 55, 3};
+        int[] b = new int[a.length];
+
+        // copy 2 elements from a, starting at a[1] to b, starting at b[3]
+        System.arraycopy(a, 1, b, 3, 2);
+        Assert.assertArrayEquals(new int[] {0, 0, 0, 22, 44, 0}, b);
+    }
+}

core-java-lang/src/test/java/com/baeldung/system/SystemNanoUnitTest.java

@@ -0,0 +1,16 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SystemNanoUnitTest {
+
+    @Test
+    public void givenSystem_whenCalledNanoTime_thenGivesTimeinResult() {
+        long startTime = System.nanoTime();
+        // do something that takes time
+        long endTime = System.nanoTime();
+
+        Assert.assertTrue(endTime - startTime < 10000);
+    }
+}

core-java-lang/src/test/java/com/baeldung/system/SystemPropertiesUnitTest.java

@@ -0,0 +1,56 @@
+package com.baeldung.system;
+
+import org.junit.Assert;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import java.util.Properties;
+
+public class SystemPropertiesUnitTest {
+
+    @Test
+    public void givenSystem_whenCalledGetProperty_thenReturnPropertyinResult() {
+        Assert.assertNotNull(System.getProperty("java.vm.vendor"));
+    }
+
+    @Test
+    public void givenSystem_whenCalledSetProperty_thenSetPropertyasResult() {
+
+        // set a particular property
+        System.setProperty("abckey", "abcvaluefoo");
+        Assert.assertEquals("abcvaluefoo", System.getProperty("abckey"));
+    }
+
+    @Test
+    public void givenSystem_whenCalledClearProperty_thenDeletePropertyasResult() {
+
+        // Delete a property
+        System.clearProperty("abckey");
+        Assert.assertNull(System.getProperty("abckey"));
+    }
+
+    @Test
+    public void givenSystem_whenCalledGetPropertyDefaultValue_thenReturnPropertyinResult() {
+
+        System.clearProperty("dbHost");
+        String myKey = System.getProperty("dbHost", "db.host.com");
+        Assert.assertEquals("db.host.com", myKey);
+    }
+
+    @Test
+    public void givenSystem_whenCalledGetProperties_thenReturnPropertiesinResult() {
+        Properties properties = System.getProperties();
+
+        Assert.assertNotNull(properties);
+    }
+
+    @Test
+    @Ignore
+    public void givenSystem_whenCalledClearProperties_thenDeleteAllPropertiesasResult() {
+
+        // Clears all system properties. Use with care!
+        System.getProperties().clear();
+
+        Assert.assertTrue(System.getProperties().isEmpty());
+    }
+}

core-java-lang/src/test/java/com/baeldung/typeerasure/TypeErasureUnitTest.java

@@ -0,0 +1,21 @@
+package com.baeldung.typeerasure;
+
+import org.junit.Test;
+
+public class TypeErasureUnitTest {
+
+    @Test(expected = ClassCastException.class)
+    public void givenIntegerStack_whenStringPushedAndAssignPoppedValueToInteger_shouldFail() {
+        IntegerStack integerStack = new IntegerStack(5);
+        Stack stack = integerStack;
+        stack.push("Hello");
+        Integer data = integerStack.pop();
+    }
+
+    @Test
+    public void givenAnyArray_whenInvokedPrintArray_shouldSucceed() {
+        Integer[] scores = new Integer[] { 100, 200, 10, 99, 20 };
+        ArrayContentPrintUtil.printArray(scores);
+    }
+
+}