Java tutorial
//package com.java2s; /* * Copyright 2011 the original author or authors. * * 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. */ import java.util.*; public class Main { public static <T> List<T> intersection(Collection<? extends Collection<T>> availableValuesByDescriptor) { List<T> result = new ArrayList<T>(); Iterator<? extends Collection<T>> iterator = availableValuesByDescriptor.iterator(); if (iterator.hasNext()) { Collection<T> firstSet = iterator.next(); result.addAll(firstSet); while (iterator.hasNext()) { Collection<T> next = iterator.next(); result.retainAll(next); } } return result; } /** * Utility for adding an iterable to a collection. * * @param t1 The collection to add to * @param t2 The iterable to add each item of to the collection * @param <T> The element type of t1 * @return t1 */ public static <T> Collection<T> addAll(Collection<T> t1, Iterable<? extends T> t2) { for (T t : t2) { t1.add(t); } return t1; } /** * Utility for adding an array to a collection. * * @param t1 The collection to add to * @param t2 The iterable to add each item of to the collection * @param <T> The element type of t1 * @return t1 */ public static <T> Collection<T> addAll(Collection<T> t1, T... t2) { Collections.addAll(t1, t2); return t1; } }