toggle boolean (#12618)

core-java-modules/core-java-lang-5/src/main/java/com/baeldung/toggleboolean/ToggleBoolean.java

@@ -0,0 +1,10 @@
+package com.baeldung.toggleboolean;
+
+public class ToggleBoolean {
+    public static Boolean toggle(Boolean b) {
+        if (b == null) {
+            return b;
+        }
+        return !b;
+    }
+}

core-java-modules/core-java-lang-5/src/test/java/com/baeldung/toggleboolean/ToggleBooleanUnitTest.java

@@ -0,0 +1,60 @@
+package com.baeldung.toggleboolean;
+
+import static org.assertj.core.api.AssertionsForClassTypes.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Test;
+
+class ToggleBooleanUnitTest {
+    @Test
+    void givenPrimitiveBoolean_whenUsingNotOperator_shouldToggleTheBoolean() {
+        boolean b = true;
+        b = !b;
+        assertFalse(b);
+
+        b = !b;
+        assertTrue(b);
+    }
+
+    @Test
+    void givenNullBoxedBoolean_whenUsingNotOperator_shouldThrowNPE() {
+        assertThatThrownBy(() -> {
+            Boolean b = null;
+            b = !b;
+        }).isInstanceOf(NullPointerException.class);
+    }
+
+    @Test
+    void givenPrimitiveBoolean_whenUsingXorOperator_shouldToggleTheBoolean() {
+        boolean b = true;
+        b ^= true;
+        assertFalse(b);
+
+        b ^= true;
+        assertTrue(b);
+    }
+
+    @Test
+    void givenBooleanObj_whenToggle_shouldGetExpectedResult() {
+        //boxed Boolean
+        Boolean b = true;
+        b = ToggleBoolean.toggle(b);
+        assertFalse(b);
+
+        b = ToggleBoolean.toggle(b);
+        assertTrue(b);
+
+        b = null;
+        b = ToggleBoolean.toggle(b);
+        assertNull(b);
+
+        //primitive boolean
+        boolean bb = true;
+        bb = ToggleBoolean.toggle(bb);
+        assertFalse(bb);
+        bb = ToggleBoolean.toggle(bb);
+        assertTrue(bb);
+    }
+}