Here you can find the source of contains(List
public static <T> boolean contains(List<T> container, List<T> list, Comparator<T> comparator)
//package com.java2s; /*// w ww . j a va2 s .c om * Sonar, open source software quality management tool. * Copyright (C) 2008-2012 SonarSource * mailto:contact AT sonarsource DOT com * * Sonar is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public * License as published by the Free Software Foundation; either * version 3 of the License, or (at your option) any later version. * * Sonar is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with Sonar; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02 */ import java.util.Comparator; import java.util.Iterator; import java.util.List; public class Main { /** * Returns true if {@code container} contains all elements from {@code list}. * Both lists must be sorted in consistency with {@code comparator}, * that is for any two sequential elements x and y: * {@code (comparator.compare(x, y) <= 0) && (comparator.compare(y, x) >= 0)}. * Running time - O(|container| + |list|). */ public static <T> boolean contains(List<T> container, List<T> list, Comparator<T> comparator) { Iterator<T> listIterator = list.iterator(); Iterator<T> containerIterator = container.iterator(); T listElement = listIterator.next(); T containerElement = containerIterator.next(); while (true) { int r = comparator.compare(containerElement, listElement); if (r == 0) { // current element from list is equal to current element from container if (!listIterator.hasNext()) { // no elements remaining in list - all were matched return true; } // next element from list also can be equal to current element from container listElement = listIterator.next(); } else if (r < 0) { // current element from list is greater than current element from container // need to check next element from container if (!containerIterator.hasNext()) { return false; } containerElement = containerIterator.next(); } else { // current element from list is less than current element from container // stop search, because current element from list would be less than any next element from container return false; } } } }