synchronized (mutex) {
        return delegate().remove(o);
      }
    }

    @Override
    public boolean removeAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().removeAll(c);
      }
    }

    @Override
    public boolean retainAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().retainAll(c);
      }

      synchronized (mutex) {
        return delegate().remove(o);
      }
    }

    @Override
    public boolean removeAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().removeAll(c);
      }
    }

    @Override
    public boolean retainAll(Collection<?> c) {
      synchronized (mutex) {
        return delegate().retainAll(c);
      }

public final class Sets {
  private Sets() {}

  /**
   * {@link AbstractSet} substitute without the potentially-quadratic {@code removeAll}
   * implementation.
   */
  abstract static class ImprovedAbstractSet<E extends @Nullable Object> extends AbstractSet<E> {
    @Override
    public boolean removeAll(Collection<?> c) {
      return removeAllImpl(this, c);
    }

    @Override
    public boolean retainAll(Collection<?> c) {

      return get((K) key).remove(value);
    }

    @SuppressWarnings("unchecked")
    @Override
    public Collection<V2> removeAll(@CheckForNull Object key) {
      return transform((K) key, fromMultimap.removeAll(key));
    }

    @Override
    public Collection<V2> replaceValues(@ParametricNullness K key, Iterable<? extends V2> values) {

	if err != nil {
		t.Fatal(err)
	}

	// Remove the object - to simulate the case where the disk was down when the object
	// was created.
	err = removeAll(pathJoin(disk.String(), bucket, object))
	if err != nil {
		t.Fatal(err)
	}

	// Checking abandoned parts should do nothing

    }.test();
  }

  public void testRemoveAll() {
    List<String> list = newArrayList("a", "b", "c", "d", "e");
    assertTrue(Iterators.removeAll(list.iterator(), newArrayList("b", "d", "f")));
    assertEquals(newArrayList("a", "c", "e"), list);
    assertFalse(Iterators.removeAll(list.iterator(), newArrayList("x", "y", "z")));
    assertEquals(newArrayList("a", "c", "e"), list);
  }

  public void testRemoveIf() {

			memberOf := cache.iamUserGroupMemberships[accessKey].ToSlice()
			for _, group := range memberOf {
				_, removeErr := removeMembersFromGroup(ctx, store, cache, group, []string{accessKey}, true)
				if removeErr == errNoSuchGroup {
					removeErr = nil
				}
				if removeErr != nil {
					return removeErr
				}
			}
		}

		// 2. Remove any derived credentials from memory
		if userType == regUser {

    }.test();
  }

  public void testRemoveAll() {
    List<String> list = newArrayList("a", "b", "c", "d", "e");
    assertTrue(Iterators.removeAll(list.iterator(), newArrayList("b", "d", "f")));
    assertEquals(newArrayList("a", "c", "e"), list);
    assertFalse(Iterators.removeAll(list.iterator(), newArrayList("x", "y", "z")));
    assertEquals(newArrayList("a", "c", "e"), list);
  }

  public void testRemoveIf() {

	xlStorageDeletedStorage, diskPath, err := newXLStorageTestSetup(t)
	if err != nil {
		t.Fatalf("Unable to create xlStorage test setup, %s", err)
	}
	// removing the disk, used to recreate disk not found error.
	os.RemoveAll(diskPath)

	// TestXLStorage for delete on an removed disk.
	// should fail with disk not found.
	err = xlStorageDeletedStorage.DeleteVol(context.Background(), "Del-Vol", false)
	if err != errDiskNotFound {

func (testServer TestServer) Stop() {
	testServer.cancel()
	testServer.Server.Close()
	testServer.Obj.Shutdown(context.Background())
	os.RemoveAll(testServer.Root)
	for _, ep := range testServer.Disks {
		for _, disk := range ep.Endpoints {
			os.RemoveAll(disk.Path)
		}
	}
}

// Truncate request to simulate unexpected EOF for a request signed using streaming signature v4.