Here you can find the source of getCommon(Collection c1, Collection c2)
private static Collection getCommon(Collection c1, Collection c2)
//package com.java2s; /*/*from w ww . j a v a 2 s .co m*/ Copyright 2014-2015 IPsoft Author: Peigen You Peigen.You@ipsoft.com This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program 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 General Public License for more details. You should have received a copy of the GNU General Public License along with this program ; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ import java.util.*; public class Main { /*********************************************************** * get Common objects between two collections */ private static Collection getCommon(Collection c1, Collection c2) { Iterator iterator = c1.iterator(); while (iterator.hasNext()) { Object o1 = iterator.next(); if (!c2.contains(o1)) iterator.remove(); } return c1; } }