introduce sorted(Comparator)

platform/platform-tests/testSrc/com/intellij/util/containers/TreeTraverserTest.java

@@ -478,6 +478,12 @@ public class TreeTraverserTest extends TestCase {
     assertEquals(Arrays.asList(1, 2, 3, 4, 5), uniqueMod5.toList()); // same results again
   }
 
+  public void testSorted() {
+    JBIterable<Integer> it1 = JBIterable.generate(1, INCREMENT).take(30);
+    JBIterable<Integer> it2 = JBIterable.generate(30, o -> o - 1).take(30).sorted(Integer::compareTo);
+    assertEquals(it1.toList(), it2.unique().toList());
+  }
+
   // TreeTraversal ----------------------------------------------
 
   @NotNull

platform/util/src/com/intellij/util/containers/JBIterable.java

@@ -844,15 +844,26 @@ public abstract class JBIterable<E> implements Iterable<E> {
   }
 
   /**
-   * Collects all items into an {@link ArrayList} and returns them as the new {@code JBIterable}.
+   * Collects all items into an {@link ArrayList} and returns it wrapped in a new {@code JBIterable}.
    * @see JBIterable#collect(Collection)
    */
   @NotNull
   public final JBIterable<E> collect() {
-    if (content instanceof ArrayList) return this;
+    if (content instanceof Collection) return this;
     return collect(ContainerUtilRt.<E>newArrayList());
   }
 
+  /**
+   * Collects all items into an {@link ArrayList}, sorts it and returns it wrapped in a new {@code JBIterable}.
+   * @see JBIterable#collect(Collection)
+   */
+  @NotNull
+  public final JBIterable<E> sorted(@NotNull Comparator<E> comparator) {
+    ArrayList<E> list = addAllTo(ContainerUtilRt.<E>newArrayList());
+    Collections.sort(list, comparator);
+    return from(list);
+  }
+
   /**
    * Returns a {@code List} containing all the elements from this iterable in
    * proper sequence.