BAEL-5873: Check If All the Variables of a Class Are Null (#13285)

* model classes. unit tests. apache lang3 dependency.

* fix PR build

core-java-modules/core-java-lang-oop-others/pom.xml

@@ -13,4 +13,12 @@
         <version>0.0.1-SNAPSHOT</version>
     </parent>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>3.12.0</version>
+        </dependency>
+    </dependencies>
+
 </project>

core-java-modules/core-java-lang-oop-others/src/main/java/com/baeldung/nullchecking/Car.java

@@ -0,0 +1,30 @@
+package com.baeldung.nullchecking;
+
+import java.util.Objects;
+import java.util.stream.Stream;
+
+public class Car {
+
+    Integer power;
+
+    Integer year;
+
+    public boolean allNull() {
+
+        if (power != null) {
+            return false;
+        }
+
+        if (year != null) {
+            return false;
+        }
+
+        return true;
+    }
+
+    public boolean allNullV2() {
+
+        return Stream.of(power, year)
+                .allMatch(Objects::isNull);
+    }
+}

core-java-modules/core-java-lang-oop-others/src/main/java/com/baeldung/nullchecking/NullChecker.java

@@ -0,0 +1,25 @@
+package com.baeldung.nullchecking;
+
+import java.lang.reflect.Field;
+import java.util.Arrays;
+import java.util.Objects;
+
+public class NullChecker {
+
+    public static boolean allNull(Object target) {
+
+        return Arrays.stream(target.getClass()
+                        .getDeclaredFields())
+                .peek(f -> f.setAccessible(true))
+                .map(f -> getFieldValue(f, target))
+                .allMatch(Objects::isNull);
+    }
+
+    private static Object getFieldValue(Field field, Object target) {
+        try {
+            return field.get(target);
+        } catch (IllegalAccessException e) {
+            throw new RuntimeException(e);
+        }
+    }
+}

core-java-modules/core-java-lang-oop-others/src/test/java/com/baeldung/nullchecking/NullCheckUnitTest.java

@@ -0,0 +1,45 @@
+package com.baeldung.nullchecking;
+
+import org.apache.commons.lang3.ObjectUtils;
+import org.junit.Test;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+public class NullCheckUnitTest {
+
+    @Test
+    public void givenNullFields_whenCheckForNullsUsingIfs_thenReturnCorrectValue(){
+        Car car = new Car();
+
+        boolean result = car.allNull();
+
+        assertTrue(result);
+    }
+
+    @Test
+    public void givenNullFields_whenCheckForNullsUsingStreams_thenReturnCorrectValue(){
+        Car car = new Car();
+
+        boolean result = car.allNullV2();
+
+        assertTrue(result);
+    }
+
+    @Test
+    public void givenNullFields_whenCheckForNullsUsingApacheCommons_thenReturnCorrectValue(){
+        Car car = new Car();
+
+        boolean result = ObjectUtils.allNull(car.power, car.year);
+
+        assertTrue(result);
+    }
+
+    @Test
+    public void givenNullFields_whenCheckForNullsUsingReflection_thenReturnCorrectValue(){
+        Car car = new Car();
+
+        boolean result = NullChecker.allNull(car);
+
+        assertTrue(result);
+    }
+}