Add toImmutableSortedSetBy to Collectors2. Resolved #1137

Signed-off-by: Ly (Harriet) Bui <lhbui@umass.edu>
eclipse · Sep 30, 2021 · 3f398a7 · 3f398a7
1 parent 2c162bc
commit 3f398a7
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diff --git a/eclipse-collections/src/main/java/org/eclipse/collections/impl/collector/Collectors2.java b/eclipse-collections/src/main/java/org/eclipse/collections/impl/collector/Collectors2.java
@@ -357,6 +357,21 @@ private Collectors2()
                 Collector.Characteristics.UNORDERED);
     }
 
+    /**
+     * <p>Returns the elements as a ImmutableSortedSet using the specified function to compare each element.</p>
+     * <p>Examples:</p>
+     * {@code ImmutableSortedSet<Integer> set1 = Interval.oneTo(5).stream().collect(Collectors2.toImmutableSortedSetBy(Object::toString));}<br>
+     * {@code ImmutableSortedSet<Integer> set2 = Interval.oneTo(5).reduceInPlace(Collectors2.toImmutableSortedSetBy(Object::toString));}
+     * <p>
+     * Equivalent to using @{@link RichIterable#toImmutableSortedSetBy(Function)}.
+     * </p>
+     * {@code ImmutableSortedSet<Integer> set = Interval.oneTo(5).toImmutableSortedSetBy(Object::toString);}
+     */
+    public static <T, V extends Comparable<? super V>> Collector<T, ?, ImmutableSortedSet<T>> toImmutableSortedSetBy(Function<? super T, ? extends V> function)
+    {
+        return Collectors2.toImmutableSortedSet(Comparators.byFunction(function));
+    }
+
     /**
      * <p>Returns the elements as a MutableBag.</p>
      * <p>Examples:</p>

diff --git a/unit-tests/src/test/java/org/eclipse/collections/impl/collector/Collectors2Test.java b/unit-tests/src/test/java/org/eclipse/collections/impl/collector/Collectors2Test.java
@@ -709,6 +709,26 @@ public void toImmutableSortedSetParallel()
         Assert.assertEquals(expected, actual2);
     }
 
+    @Test
+    public void toImmutableSortedSetBy()
+    {
+        MutableSortedSet<Integer> expected = SMALL_INTERVAL.toSortedSetBy(Object::toString);
+        ImmutableSortedSet<Integer> actual = this.smallData.stream().collect(Collectors2.toImmutableSortedSetBy(Object::toString));
+        Assert.assertEquals(expected, actual);
+        ImmutableSortedSet<Integer> actual2 = SMALL_INTERVAL.reduceInPlace(Collectors2.toImmutableSortedSetBy(Object::toString));
+        Assert.assertEquals(expected, actual2);
+    }
+
+    @Test
+    public void toImmutableSortedSetByParallel()
+    {
+        MutableSortedSet<Integer> expected = LARGE_INTERVAL.toSortedSetBy(Object::toString);
+        ImmutableSortedSet<Integer> actual = this.bigData.parallelStream().collect(Collectors2.toImmutableSortedSetBy(Object::toString));
+        Assert.assertEquals(expected, actual);
+        ImmutableSortedSet<Integer> actual2 = LARGE_INTERVAL.reduceInPlace(Collectors2.toImmutableSortedSetBy(Object::toString));
+        Assert.assertEquals(expected, actual2);
+    }
+
     @Test
     public void toSortedBag()
     {