diff --git a/src/changes/changes.xml b/src/changes/changes.xml index c7d8c988b..0da4fbd19 100644 --- a/src/changes/changes.xml +++ b/src/changes/changes.xml @@ -21,6 +21,9 @@ + + Add hashCode method to CollectionUtils that supports an equator parameter. + Fix checkstyle issues regarding missing newline at end of file, and CRLF vs LF. diff --git a/src/main/java/org/apache/commons/collections4/CollectionUtils.java b/src/main/java/org/apache/commons/collections4/CollectionUtils.java index 2b73511a7..4c2f4167f 100644 --- a/src/main/java/org/apache/commons/collections4/CollectionUtils.java +++ b/src/main/java/org/apache/commons/collections4/CollectionUtils.java @@ -643,6 +643,33 @@ public class CollectionUtils { return isEqualCollection(collect(a, transformer), collect(b, transformer)); } + /** + * Returns the hash code of the input collection using the hash method of an equator. + * + *

+ * Returns 0 if the input collection is {@code null}. + *

+ * + * @param the element type + * @param collection the input collection + * @param equator the equator used for generate hashCode + * @return the hash code of the input collection using the hash method of an equator + * @throws NullPointerException if the equator is {@code null} + * @since 4.5 + */ + public static int hashCode(final Collection collection, + final Equator equator) { + Objects.requireNonNull(equator, "equator"); + if (null == collection) { + return 0; + } + int hashCode = 1; + for (final E e : collection) { + hashCode = 31 * hashCode + equator.hash(e); + } + return hashCode; + } + /** * Wraps another object and uses the provided Equator to implement * {@link #equals(Object)} and {@link #hashCode()}. diff --git a/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java b/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java index 7d1bd98f2..4922a9176 100644 --- a/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java +++ b/src/test/java/org/apache/commons/collections4/CollectionUtilsTest.java @@ -37,6 +37,7 @@ import java.util.Iterator; import java.util.LinkedList; import java.util.List; import java.util.Map; +import java.util.Objects; import java.util.Queue; import java.util.Set; import java.util.SortedMap; @@ -741,6 +742,52 @@ public class CollectionUtilsTest extends MockTestCase { CollectionUtils.isEqualCollection(collectionA, collectionA, null); } + @Test + public void testHashCode() { + final Equator e = new Equator() { + @Override + public boolean equate(final Integer o1, final Integer o2) { + if (o1 % 2 == 0 ^ o2 % 2 == 0) { + return false; + } + return true; + } + + @Override + public int hash(final Integer o) { + return o == null ? 0 : Objects.hashCode(o); + } + }; + + assertEquals(collectionA.hashCode(), CollectionUtils.hashCode(collectionA, e)); + } + + @Test + public void testHashCodeNullCollection() { + final Equator e = new Equator() { + @Override + public boolean equate(final Integer o1, final Integer o2) { + if (o1 % 2 == 0 ^ o2 % 2 == 0) { + return false; + } + return true; + } + + @Override + public int hash(final Integer o) { + return o == null ? 0 : Objects.hashCode(o); + } + }; + + final Collection collection = null; + assertEquals(0, CollectionUtils.hashCode(collection, e)); + } + + @Test(expected=NullPointerException.class) + public void testHashCodeNullEquator() { + CollectionUtils.hashCode(collectionB, null); + } + @Test(expected = NullPointerException.class) public void testIsEqualCollectionNullColl1() { final Collection list = new ArrayList<>(1); @@ -1073,7 +1120,7 @@ public class CollectionUtilsTest extends MockTestCase { CollectionUtils.get(array, 2); } - @Test(expected=IllegalArgumentException.class) + @Test(expected = IllegalArgumentException.class) public void getFromObject() throws Exception { // Invalid object final Object obj = new Object();