Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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. */ package org.apache.commons.collections4.bag; import java.io.IOException; import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.io.Serializable; import java.util.Collection; import java.util.HashMap; /** * Implements {@link Bag}, using a {@link HashMap} to provide the * data storage. This is the standard implementation of a bag. * <p> * A {@link Bag} stores each object in the collection together with a * count of occurrences. Extra methods on the interface allow multiple copies * of an object to be added or removed at once. It is important to read the * interface javadoc carefully as several methods violate the * {@link Collection} interface specification. * * @since 3.0 (previously in main package v2.0) * @version $Id: HashBag.java 1543928 2013-11-20 20:15:35Z tn $ */ public class HashBag<E> extends AbstractMapBag<E> implements Serializable { /** Serial version lock */ private static final long serialVersionUID = -6561115435802554013L; /** * Constructs an empty {@link HashBag}. */ public HashBag() { super(new HashMap<E, MutableInteger>()); } /** * Constructs a bag containing all the members of the given collection. * * @param coll a collection to copy into this bag */ public HashBag(final Collection<? extends E> coll) { this(); addAll(coll); } //----------------------------------------------------------------------- /** * Write the bag out using a custom routine. */ private void writeObject(final ObjectOutputStream out) throws IOException { out.defaultWriteObject(); super.doWriteObject(out); } /** * Read the bag in using a custom routine. */ private void readObject(final ObjectInputStream in) throws IOException, ClassNotFoundException { in.defaultReadObject(); super.doReadObject(new HashMap<E, MutableInteger>(), in); } }