Here you can find the source of union(Collection
| Parameter | Description |
|---|---|
| c1 | the first collection to add elements from. |
| c2 | the second collection to add elements from. |
| E | the type of the collections elements. |
public static <E> List<E> union(Collection<E> c1, Collection<E> c2)
//package com.java2s; /*//from ww w . ja v a 2 s. com * Copyright (c) 2013, SRI International * All rights reserved. * Licensed under the The BSD 3-Clause License; * you may not use this file except in compliance with the License. * You may obtain a copy of the License at: * * http://opensource.org/licenses/BSD-3-Clause * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * Neither the name of the aic-util nor the names of its * contributors may be used to endorse or promote products derived from * this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ import java.util.Arrays; import java.util.Collection; import java.util.Iterator; import java.util.LinkedHashMap; import java.util.LinkedList; import java.util.List; import java.util.Map; public class Main { /** * Adds all elements of two collections to a new LinkedList. * * @param c1 * the first collection to add elements from. * @param c2 * the second collection to add elements from. * @return a LinkedList containing the elements from both input collections. * @param <E> * the type of the collections elements. */ public static <E> List<E> union(Collection<E> c1, Collection<E> c2) { List<E> result = new LinkedList<E>(); result.addAll(c1); result.addAll(c2); return result; } /** * Same as {@link #union(Iterator)} applied to given collection's iterator. * @param maps the collection of maps * @param <K> the type of keys * @param <V> the type of values * @return a new map with all entries from all maps in a collection */ public static <K, V> Map<K, V> union(Collection<Map<K, V>> maps) { return union(maps.iterator()); } /** * Returns a new map with all entries from all maps in an iterator's range. * @param mapsIterator the maps iterator * @param <K> the type of keys * @param <V> the type of values * @return a new map with all entries from all maps in an iterator's range */ public static <K, V> Map<K, V> union(Iterator<Map<K, V>> mapsIterator) { return putAllFromAll(new LinkedHashMap<K, V>(), mapsIterator); } /** * Adds all elements of iterator's range to collection. * * @param c * the collection to add the iterator's range to. * @param i * the iterator whose range is to be added to the given * collection. * @return the given collection. * @param <T> * the type of the elements given. * @param <C> the type of the collection */ public static <T, C extends Collection<T>> C addAll(C c, Iterator<T> i) { while (i.hasNext()) { c.add(i.next()); } return c; } /** * Construct an iterator of the given type ranging over provided elements. * * @param elements * the elements to construct the List from. * @return an iterator over the received arguments. * @param <T> * the type of elements the iterator will range over. */ public static <T> Iterator<T> iterator(T... elements) { return Arrays.asList(elements).iterator(); } /** * Puts all entries from all maps in the range of an iterator to a given map. * @param map the map * @param mapsIterator the maps iterator * @param <K> the type of keys * @param <V> the type of values * @return the given map with all entries from all maps in interator's range */ public static <K, V> Map<K, V> putAllFromAll(Map<K, V> map, Iterator<Map<K, V>> mapsIterator) { for (Map<K, V> eachMap : in(mapsIterator)) { map.putAll(eachMap); } return map; } /** * Adapts an {@link Iterator} to an {@link Iterable} for use in enhanced for * loops. If {@link Iterable#iterator()} is invoked more than once, an * {@link IllegalStateException} is thrown. * @param iterator the iterator * @param <T> the type of elements * @return the iterable for iterator */ public static <T> Iterable<T> in(final Iterator<T> iterator) { assert iterator != null; class SingleUseIterable implements Iterable<T> { private boolean used = false; @Override public Iterator<T> iterator() { if (used) { throw new IllegalStateException("SingleUseIterable already invoked"); } used = true; return iterator; } } return new SingleUseIterable(); } /** * @param map * a map. * @param keysAndValues * a sequence of key and value pairs to be placed into a given Map. * * @return the received arguments (interpreted as a sequence of key and * value pairs) in a given map. * @param <K> * the type of the Map's key. * @param <V> * the type of the Map's value. */ @SuppressWarnings("unchecked") public static <K, V> Map<K, V> putAll(Map<K, V> map, Object... keysAndValues) { int i = 0; while (i != keysAndValues.length) { map.put((K) keysAndValues[i], (V) keysAndValues[i + 1]); i += 2; } return map; } }