Added containsBy to RichIterable. Closes #919.

Signed-off-by: Donald Raab <Donald.Raab@bnymellon.com>
eclipse · Jul 7, 2020 · 759d4f5 · 759d4f5
1 parent cb8b03c
commit 759d4f5
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diff --git a/eclipse-collections-api/src/main/java/org/eclipse/collections/api/RichIterable.java b/eclipse-collections-api/src/main/java/org/eclipse/collections/api/RichIterable.java
@@ -17,6 +17,7 @@
 import java.util.LongSummaryStatistics;
 import java.util.Map;
 import java.util.NoSuchElementException;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.function.BiConsumer;
 import java.util.function.BinaryOperator;
@@ -179,6 +180,23 @@ default T getOnly()
      */
     boolean contains(Object object);
 
+    /**
+     * Returns true if the iterable has an element which responds true to element.equals(value)
+     * after applying the specified function to the element.
+     *
+     * @since 10.3
+     */
+    default <V> boolean containsBy(
+            Function<? super T, ? extends V> function,
+            V value)
+    {
+        Objects.requireNonNull(function);
+        Predicate<? super T> predicate = null == value
+                ? each -> null == function.valueOf(each)
+                : each -> value.equals(function.valueOf(each));
+        return this.anySatisfy(predicate);
+    }
+
     /**
      * Returns true if all elements in source are contained in this collection.
      *

diff --git a/unit-tests/src/test/java/org/eclipse/collections/impl/AbstractRichIterableTestCase.java b/unit-tests/src/test/java/org/eclipse/collections/impl/AbstractRichIterableTestCase.java
@@ -160,6 +160,7 @@
 import org.eclipse.collections.impl.set.mutable.primitive.ShortHashSet;
 import org.eclipse.collections.impl.set.sorted.mutable.TreeSortedSet;
 import org.eclipse.collections.impl.test.Verify;
+import org.eclipse.collections.impl.tuple.Tuples;
 import org.eclipse.collections.impl.tuple.primitive.PrimitiveTuples;
 import org.junit.Assert;
 import org.junit.Test;
@@ -192,6 +193,31 @@ public void contains()
         Assert.assertFalse(collection.contains(5));
     }
 
+    @Test
+    public void containsBy()
+    {
+        MutableList<Pair<Integer, String>> list =
+                Lists.mutable.with(
+                        Tuples.pair(1, "1"),
+                        Tuples.pair(2, "2"),
+                        Tuples.pair(3, null));
+
+        Assert.assertTrue(
+                list.containsBy(Pair::getTwo, "2"));
+        Assert.assertFalse(
+                list.containsBy(Pair::getTwo, "3"));
+        Assert.assertTrue(
+                list.containsBy(Pair::getTwo, null));
+        Assert.assertFalse(
+                list.containsBy(Pair::getOne, null));
+        Assert.assertFalse(
+                list.newEmpty().containsBy(Pair::getOne, null));
+        Assert.assertFalse(
+                list.newEmpty().containsBy(Pair::getOne, "2"));
+        Verify.assertThrows(NullPointerException.class, () ->
+                list.newEmpty().containsBy(null, "2"));
+    }
+
     @Test
     public void containsAllIterable()
     {