diff --git a/core-java-modules/core-java-lang-6/src/main/java/com/baeldung/returnfirstnonnull/LazyEvaluate.java b/core-java-modules/core-java-lang-6/src/main/java/com/baeldung/returnfirstnonnull/LazyEvaluate.java new file mode 100644 index 0000000000..faa6cce465 --- /dev/null +++ b/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"; + } +} \ No newline at end of file diff --git a/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonempty/ReturnFirstNonEmptyOptionalUnitTest.java b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonempty/ReturnFirstNonEmptyOptionalUnitTest.java new file mode 100644 index 0000000000..f2ea8f74e3 --- /dev/null +++ b/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> optionals; + + @BeforeEach + public void init() { + optionals = Arrays.asList(Optional. empty(), Optional.of("first non empty"), Optional.of("second non empty")); + } + + @Test + void givenListOfOptionals_whenStreaming_thenReturnFirstNonEmpty() { + Optional object = optionals.stream() + .filter(Optional::isPresent) + .map(Optional::get) + .findFirst(); + + assertThat(object).contains("first non empty"); + } +} \ No newline at end of file diff --git a/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullLazyEvaluateUnitTest.java b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullLazyEvaluateUnitTest.java new file mode 100644 index 0000000000..af88545170 --- /dev/null +++ b/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 object = Stream.> 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); + } +} \ No newline at end of file diff --git a/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullUnitTest.java b/core-java-modules/core-java-lang-6/src/test/java/com/baeldung/returnfirstnonnull/ReturnFirstNonNullUnitTest.java new file mode 100644 index 0000000000..124de5843c --- /dev/null +++ b/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 objects; + + @BeforeEach + public void init() { + objects = Arrays.asList(null, "first non null", "second nun null"); + } + + @Test + void givenListOfObjects_whenFilterIsLambdaNullCheckInStream_thenReturnFirstNonNull() { + Optional object = objects.stream() + .filter(o -> o != null) + .findFirst(); + + assertThat(object).contains("first non null"); + } + + @Test + void givenListOfObjects_whenFilterIsMethodRefNullCheckInStream_thenReturnFirstNonNull() { + Optional 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); + } +} \ No newline at end of file