return first non null and non empty optional unit tests

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/returnfirstnonempty/ReturnFirstNonEmptyOptionalUnitTest.java

@@ -0,0 +1,37 @@
+package returnfirstnonempty;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ReturnFirstNonEmptyOptionalUnitTest {
+
+    private List<Optional<Object>> optionals;
+
+    @Before
+    public void init() {
+        optionals = Arrays.asList(
+            Optional.empty(),
+            Optional.of(new Object()),
+            Optional.empty()
+        );
+    }
+
+    @Test
+    public void givenListOfOptionals_thenReturnFirstNonEmpty() {
+        Object object = optionals
+            .stream()
+            .filter(Optional::isPresent)
+            .map(Optional::get)
+            .findFirst();
+
+        assertTrue(object != null);
+        assertEquals(optionals.get(1), object);
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullLazyEvaluateUnitTest.java

@@ -0,0 +1,69 @@
+package returnfirstnonull;
+
+import java.util.Objects;
+import java.util.Optional;
+import java.util.function.Supplier;
+import java.util.stream.Stream;
+
+import org.apache.commons.lang3.ObjectUtils;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ReturnFirstNonNullLazyEvaluateUnitTest {
+
+    private static Object METHOD_B_OBJECT = new Object();
+
+    private Object methodA() { return null; }
+
+    private Object methodB() { return METHOD_B_OBJECT; }
+
+    private Object methodC() { return null; }
+
+    @Test
+    public void givenChainOfMethods_thenLazilyEvaluateMethodsUntilFirstNonNull() {
+        Object object = methodA();
+        if(object == null)
+            object = methodB();
+
+        if(object == null)
+            object = methodC();
+
+        assertTrue(object != null);
+        assertEquals(METHOD_B_OBJECT, object);  
+    }
+
+    @Test
+    public void givenChainOfMethods_whenUsingSupplierInterface_thenLazilyEvaluateMethodsUntilFirstNonNull() {
+        Optional<Object> object = Stream
+            .<Supplier<Object>>of(
+                this::methodA, 
+                this::methodB,
+                this::methodC)
+            .map(Supplier::get)
+            .filter(Objects::nonNull)
+            .findFirst();
+
+        assertTrue(object.isPresent());
+        assertEquals(METHOD_B_OBJECT, object.get());
+    }
+
+    @Test
+    public void givenTwoObjects_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        Object object1 = methodA();
+        Object object = ObjectUtils.getIfNull(object1, this::methodB);
+
+        assertTrue(object != null);
+        assertEquals(METHOD_B_OBJECT, object);
+    }
+
+    @Test
+    public void givenChainOfMethods_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        Object object = ObjectUtils.getFirstNonNull(this::methodA, this::methodB, this::methodC);
+
+        assertTrue(object != null);
+        assertEquals(METHOD_B_OBJECT, object);
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullUnitTest.java

@@ -0,0 +1,108 @@
+package returnfirstnonull;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+import java.util.Optional;
+
+import org.apache.commons.lang3.ObjectUtils;
+
+import org.junit.Before;
+import org.junit.Test;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
+
+public class ReturnFirstNonNullUnitTest {
+
+    private List<Object> objects;
+
+    @Before
+    public void init() {
+        objects = Arrays.asList(
+            null,
+            new Object(),
+            new Object()
+        );
+    }
+
+    @Test
+    public void givenListOfObjects_whenIteratingWithForLoop_thenReturnFirstNonNull() {
+        Object object = null; 
+        for(int i = 0; i < objects.size(); i++) {
+            if(objects.get(i) != null) {
+                object = objects.get(i);
+                break;
+            }
+        }
+
+        assertTrue(object != null);
+        assertEquals(objects.get(1), object);
+    }
+
+    @Test
+    public void givenListOfObjects_whenIteratingWithEnhancedForLoop_thenReturnFirstNonNull() {
+        Object object = null; 
+        for(Object o: objects) {
+            if(o != null) {
+                object = o;
+                break;
+            }
+        }
+
+        assertTrue(object != null);
+        assertEquals(objects.get(1), object);
+    }
+
+    @Test
+    public void givenListOfObjects_whenFilterIsLambdaNullCheck_thenReturnFirstNonNull() {
+        Optional<Object> object = objects
+            .stream()
+            .filter(o -> o != null)
+            .findFirst();
+
+        assertTrue(object.isPresent());
+        assertEquals(objects.get(1), object.get());
+    }
+
+    @Test
+    public void givenListOfObjects_whenFilterIsMethodRefNullCheck_thenReturnFirstNonNull() {
+        Optional<Object> object = objects
+            .stream()
+            .filter(Objects::nonNull)
+            .findFirst();
+
+        assertTrue(object.isPresent());
+        assertEquals(objects.get(1), object.get());
+    }
+
+    @Test
+    public void givenListOfObjects_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        Object object = ObjectUtils.firstNonNull(objects.toArray());
+
+        assertTrue(object != null);
+        assertEquals(objects.get(1), object);
+    }
+
+    @Test
+    public void givenTwoObjects_whenUsingGoogleGuava_thenReturnFirstNonNull() {
+        Object object1 = null;
+        Object object2 = new Object();
+        Object object = MoreObjects.firstNonNull(object1, object2);
+
+        assertTrue(object != null);
+        assertEquals(object2, object);
+    }
+
+    @Test
+    public void givenListOfObjects_whenUsingGoogleGuava_thenReturnFirstNonNull() {
+        Object object = Iterables.find(objects, Predicates.notNull());
+
+        assertTrue(object != null);
+        assertEquals(objects.get(1), object);
+    }
+}