Here you can find the source of isSubset(Collection> subset, Collection> of)
public static boolean isSubset(Collection<?> subset, Collection<?> of)
//package com.java2s; /*//from w w w . j a v a2 s.c o m * CollectionUtils.java * * Copyright (C) 2012-2014 LucasEasedUp * * 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 3 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, see <http://www.gnu.org/licenses/>. */ import java.util.Collection; public class Main { public static boolean isSubset(Collection<?> subset, Collection<?> of) { for (Object obj : subset) { if (!of.contains(obj)) { return false; } } return true; } }