Here you can find the source of retainAll(final List> list, final Collection
public static void retainAll(final List<?> list, final Collection<Integer> indices)
//package com.java2s; /******************************************************************************* * Copyright (c) 2010-2014 Alexander Kerner. All rights reserved. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License.// ww w . j a v a 2 s. com ******************************************************************************/ import java.util.Collection; import java.util.List; import java.util.ListIterator; public class Main { public static void retainAll(final List<?> list, final Collection<Integer> indices) { final ListIterator<?> it = list.listIterator(); while (it.hasNext()) { final int index = it.nextIndex(); it.next(); if (indices.contains(index)) { // ok } else { it.remove(); } } } }