From deb27c1e3bbd7b2dc6416a70a0004a1f359a8f71 Mon Sep 17 00:00:00 2001 From: Tonnix Date: Sun, 29 Jul 2018 18:07:16 +0300 Subject: [PATCH] Added PR files for BAEL-2031 (#4844) * Added source files for BAEL-2031 * Added test files for BAEL-2031 --- ...lectionStreamsUsingCommonsEmptyIfNull.java | 19 +++++++ ...ionStreamsUsingJava8OptionalContainer.java | 21 ++++++++ ...ctionStreamsUsingNullDereferenceCheck.java | 20 +++++++ ...treamsUsingCommonsEmptyIfNullUnitTest.java | 41 ++++++++++++++ ...msUsingJava8OptionalContainerUnitTest.java | 53 +++++++++++++++++++ ...eamsUsingNullDereferenceCheckUnitTest.java | 45 ++++++++++++++++ 6 files changed, 199 insertions(+) create mode 100644 core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNull.java create mode 100644 core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainer.java create mode 100644 core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheck.java create mode 100644 core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNullUnitTest.java create mode 100644 core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainerUnitTest.java create mode 100644 core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheckUnitTest.java diff --git a/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNull.java b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNull.java new file mode 100644 index 0000000000..7587cc6834 --- /dev/null +++ b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNull.java @@ -0,0 +1,19 @@ +package com.baeldung.nullsafecollectionstreams; + +import java.util.Collection; +import java.util.stream.Stream; +import static org.apache.commons.collections4.CollectionUtils.emptyIfNull; + +public class NullSafeCollectionStreamsUsingCommonsEmptyIfNull { + + /** + * This method shows how to make a null safe stream from a collection through the use of + * emptyIfNull() method from Apache Commons CollectionUtils library + * + * @param collection The collection that is to be converted into a stream + * @return The stream that has been created from the collection or an empty stream if the collection is null + */ + public Stream collectionAsStream(Collection collection) { + return emptyIfNull(collection).stream(); + } +} diff --git a/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainer.java b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainer.java new file mode 100644 index 0000000000..ae8e399d53 --- /dev/null +++ b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainer.java @@ -0,0 +1,21 @@ +package com.baeldung.nullsafecollectionstreams; + +import java.util.Collection; +import java.util.Optional; +import java.util.stream.Stream; + +public class NullSafeCollectionStreamsUsingJava8OptionalContainer { + + /** + * This method shows how to make a null safe stream from a collection through the use of + * Java SE 8’s Optional Container + * + * @param collection The collection that is to be converted into a stream + * @return The stream that has been created from the collection or an empty stream if the collection is null + */ + public Stream collectionAsStream(Collection collection) { + return Optional.ofNullable(collection) + .map(Collection::stream) + .orElseGet(Stream::empty); + } +} diff --git a/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheck.java b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheck.java new file mode 100644 index 0000000000..63b6d34f11 --- /dev/null +++ b/core-java-8/src/main/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheck.java @@ -0,0 +1,20 @@ +package com.baeldung.nullsafecollectionstreams; + +import java.util.Collection; +import java.util.stream.Stream; + +public class NullSafeCollectionStreamsUsingNullDereferenceCheck { + + /** + * This method shows how to make a null safe stream from a collection through the use of a check + * to prevent null dereferences + * + * @param collection The collection that is to be converted into a stream + * @return The stream that has been created from the collection or an empty stream if the collection is null + */ + public Stream collectionAsStream(Collection collection) { + return collection == null ? Stream.empty() : collection.stream(); + } + + +} diff --git a/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNullUnitTest.java b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNullUnitTest.java new file mode 100644 index 0000000000..f68df2c821 --- /dev/null +++ b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingCommonsEmptyIfNullUnitTest.java @@ -0,0 +1,41 @@ +package com.baeldung.nullsafecollectionstreams; + +import java.util.Arrays; +import java.util.Collection; +import java.util.Iterator; +import java.util.stream.Stream; +import org.junit.Test; +import static org.junit.Assert.*; + + +public class NullSafeCollectionStreamsUsingCommonsEmptyIfNullUnitTest { + + private final NullSafeCollectionStreamsUsingCommonsEmptyIfNull instance = + new NullSafeCollectionStreamsUsingCommonsEmptyIfNull(); + + @Test + public void whenCollectionIsNull_thenExpectAnEmptyStream() { + Collection collection = null; + Stream expResult = Stream.empty(); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + + } + + @Test + public void whenCollectionHasElements_thenExpectAStreamOfExactlyTheSameElements() { + + Collection collection = Arrays.asList("a", "b", "c"); + Stream expResult = Arrays.stream(new String[] { "a", "b", "c" }); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + } + + private static void assertStreamEquals(Stream s1, Stream s2) { + Iterator iter1 = s1.iterator(), iter2 = s2.iterator(); + while (iter1.hasNext() && iter2.hasNext()) + assertEquals(iter1.next(), iter2.next()); + assert !iter1.hasNext() && !iter2.hasNext(); + } + +} diff --git a/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainerUnitTest.java b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainerUnitTest.java new file mode 100644 index 0000000000..4df3482633 --- /dev/null +++ b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingJava8OptionalContainerUnitTest.java @@ -0,0 +1,53 @@ +/* + * To change this license header, choose License Headers in Project Properties. + * To change this template file, choose Tools | Templates + * and open the template in the editor. + */ +package com.baeldung.nullsafecollectionstreams; + +import java.util.Arrays; +import java.util.Collection; +import java.util.Iterator; +import java.util.stream.Stream; +import org.junit.After; +import org.junit.AfterClass; +import org.junit.Before; +import org.junit.BeforeClass; +import org.junit.Test; +import static org.junit.Assert.*; + +/** + * + * @author Kwaje Anthony + */ +public class NullSafeCollectionStreamsUsingJava8OptionalContainerUnitTest { + + private final NullSafeCollectionStreamsUsingJava8OptionalContainer instance = + new NullSafeCollectionStreamsUsingJava8OptionalContainer(); + + @Test + public void whenCollectionIsNull_thenExpectAnEmptyStream() { + Collection collection = null; + Stream expResult = Stream.empty(); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + + } + + @Test + public void whenCollectionHasElements_thenExpectAStreamOfExactlyTheSameElements() { + + Collection collection = Arrays.asList("a", "b", "c"); + Stream expResult = Arrays.stream(new String[] { "a", "b", "c" }); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + } + + private static void assertStreamEquals(Stream s1, Stream s2) { + Iterator iter1 = s1.iterator(), iter2 = s2.iterator(); + while (iter1.hasNext() && iter2.hasNext()) + assertEquals(iter1.next(), iter2.next()); + assert !iter1.hasNext() && !iter2.hasNext(); + } + +} diff --git a/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheckUnitTest.java b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheckUnitTest.java new file mode 100644 index 0000000000..ddb4dcdc12 --- /dev/null +++ b/core-java-8/src/test/java/com/baeldung/nullsafecollectionstreams/NullSafeCollectionStreamsUsingNullDereferenceCheckUnitTest.java @@ -0,0 +1,45 @@ + +package com.baeldung.nullsafecollectionstreams; + +import java.util.Arrays; +import java.util.Collection; +import java.util.Iterator; +import java.util.stream.Stream; +import org.junit.Test; +import static org.junit.Assert.*; + +/** + * + * @author Kwaje Anthony + */ +public class NullSafeCollectionStreamsUsingNullDereferenceCheckUnitTest { + + private final NullSafeCollectionStreamsUsingNullDereferenceCheck instance = + new NullSafeCollectionStreamsUsingNullDereferenceCheck(); + + @Test + public void whenCollectionIsNull_thenExpectAnEmptyStream() { + Collection collection = null; + Stream expResult = Stream.empty(); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + + } + + @Test + public void whenCollectionHasElements_thenExpectAStreamOfExactlyTheSameElements() { + + Collection collection = Arrays.asList("a", "b", "c"); + Stream expResult = Arrays.stream(new String[] { "a", "b", "c" }); + Stream result = instance.collectionAsStream(collection); + assertStreamEquals(expResult, result); + } + + private static void assertStreamEquals(Stream s1, Stream s2) { + Iterator iter1 = s1.iterator(), iter2 = s2.iterator(); + while (iter1.hasNext() && iter2.hasNext()) + assertEquals(iter1.next(), iter2.next()); + assert !iter1.hasNext() && !iter2.hasNext(); + } + +}