Merge pull request #15113 from danielmcnally285/danielmcnally285_return_first_non_null

BAEL-7010 - return first non null

core-java-modules/core-java-lang-6/src/main/java/com/baeldung/returnfirstnonnull/LazyEvaluate.java

@@ -0,0 +1,16 @@
+package com.baeldung.returnfirstnonnull;
+
+class LazyEvaluate {
+
+    String methodA() {
+        return null;
+    }
+
+    String methodB() {
+        return "first non null";
+    }
+
+    String methodC() {
+        return "second non null";
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonempty/ReturnFirstNonEmptyOptionalUnitTest.java

@@ -0,0 +1,30 @@
+package com.baeldung.returnfirstnonempty;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class ReturnFirstNonEmptyOptionalUnitTest {
+
+    private List<Optional<String>> optionals;
+
+    @BeforeEach
+    public void init() {
+        optionals = Arrays.asList(Optional.<String> empty(), Optional.of("first non empty"), Optional.of("second non empty"));
+    }
+
+    @Test
+    void givenListOfOptionals_whenStreaming_thenReturnFirstNonEmpty() {
+        Optional<String> object = optionals.stream()
+            .filter(Optional::isPresent)
+            .map(Optional::get)
+            .findFirst();
+
+        assertThat(object).contains("first non empty");
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullLazyEvaluateUnitTest.java

@@ -0,0 +1,77 @@
+package com.baeldung.returnfirstnonnull;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+
+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.jupiter.api.Test;
+import org.mockito.Mockito;
+
+public class ReturnFirstNonNullLazyEvaluateUnitTest {
+
+    private final LazyEvaluate spy = Mockito.spy(new LazyEvaluate());
+
+    @Test
+    void givenChainOfMethods_whenUsingIfStatements_thenLazilyEvaluateMethodsUntilFirstNonNull() {
+        String object = spy.methodA();
+        if (object == null) {
+            object = spy.methodB();
+        }
+
+        if (object == null) {
+            object = spy.methodC();
+        }
+
+        assertEquals("first non null", object);
+        verify(spy, times(1)).methodA();
+        verify(spy, times(1)).methodB();
+        verify(spy, times(0)).methodC();
+    }
+
+    @Test
+    void givenChainOfMethods_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        String object = ObjectUtils.getFirstNonNull(spy::methodA, spy::methodB, spy::methodC);
+
+        assertEquals("first non null", object);
+        verify(spy, times(1)).methodA();
+        verify(spy, times(1)).methodB();
+        verify(spy, times(0)).methodC();
+    }
+
+    @Test
+    void givenChainOfMethods_whenUsingSupplierInterface_thenLazilyEvaluateMethodsUntilFirstNonNull() {
+        Optional<String> object = Stream.<Supplier<String>> of(spy::methodA, spy::methodB, spy::methodC)
+            .map(Supplier::get)
+            .filter(Objects::nonNull)
+            .findFirst();
+
+        assertThat(object).contains("first non null");
+        verify(spy, times(1)).methodA();
+        verify(spy, times(1)).methodB();
+        verify(spy, times(0)).methodC();
+    }
+
+    @Test
+    void givenNonNullObjectAndFallbackMethod_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        String nonNullObject = spy.methodB();
+        String object = ObjectUtils.getIfNull(nonNullObject, spy::methodC);
+
+        assertEquals("first non null", object);
+        verify(spy, times(0)).methodC();
+    }
+
+    @Test
+    void givenNullObjectAndFallbackMethod_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        String nullObject = null;
+        String object = ObjectUtils.getIfNull(nullObject, spy::methodB);
+
+        assertEquals("first non null", object);
+    }
+}

core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullUnitTest.java

@@ -0,0 +1,81 @@
+package com.baeldung.returnfirstnonnull;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+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.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Predicates;
+import com.google.common.collect.Iterables;
+
+public class ReturnFirstNonNullUnitTest {
+
+    private List<String> objects;
+
+    @BeforeEach
+    public void init() {
+        objects = Arrays.asList(null, "first non null", "second nun null");
+    }
+
+    @Test
+    void givenListOfObjects_whenFilterIsLambdaNullCheckInStream_thenReturnFirstNonNull() {
+        Optional<String> object = objects.stream()
+            .filter(o -> o != null)
+            .findFirst();
+
+        assertThat(object).contains("first non null");
+    }
+
+    @Test
+    void givenListOfObjects_whenFilterIsMethodRefNullCheckInStream_thenReturnFirstNonNull() {
+        Optional<String> object = objects.stream()
+            .filter(Objects::nonNull)
+            .findFirst();
+
+        assertThat(object).contains("first non null");
+    }
+
+    @Test
+    void givenListOfObjects_whenIteratingWithForLoop_thenReturnFirstNonNull() {
+        String object = null;
+        for (int i = 0; i < objects.size(); i++) {
+            if (objects.get(i) != null) {
+                object = objects.get(i);
+                break;
+            }
+        }
+
+        assertEquals("first non null", object);
+    }
+
+    @Test
+    void givenListOfObjects_whenUsingApacheCommonsLang3_thenReturnFirstNonNull() {
+        String object = ObjectUtils.firstNonNull(objects.toArray(new String[0]));
+
+        assertEquals("first non null", object);
+    }
+
+    @Test
+    void givenListOfObjects_whenUsingGoogleGuavaIterables_thenReturnFirstNonNull() {
+        String object = Iterables.find(objects, Predicates.notNull());
+
+        assertEquals("first non null", object);
+    }
+
+    @Test
+    void givenTwoObjects_whenUsingGoogleGuavaMoreObjects_thenReturnFirstNonNull() {
+        String nullObject = null;
+        String nonNullObject = "first non null";
+        String object = MoreObjects.firstNonNull(nullObject, nonNullObject);
+
+        assertEquals("first non null", object);
+    }
+}