001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.bag; 018 019 import java.io.IOException; 020 import java.io.ObjectInputStream; 021 import java.io.ObjectOutputStream; 022 import java.io.Serializable; 023 import java.util.Collection; 024 import java.util.HashMap; 025 026 import org.apache.commons.collections.Bag; 027 028 /** 029 * Implements <code>Bag</code>, using a <code>HashMap</code> to provide the 030 * data storage. This is the standard implementation of a bag. 031 * <p> 032 * A <code>Bag</code> stores each object in the collection together with a 033 * count of occurrences. Extra methods on the interface allow multiple copies 034 * of an object to be added or removed at once. It is important to read the 035 * interface javadoc carefully as several methods violate the 036 * <code>Collection</code> interface specification. 037 * 038 * @since Commons Collections 3.0 (previously in main package v2.0) 039 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 040 * 041 * @author Chuck Burdick 042 * @author Stephen Colebourne 043 */ 044 public class HashBag 045 extends AbstractMapBag implements Bag, Serializable { 046 047 /** Serial version lock */ 048 private static final long serialVersionUID = -6561115435802554013L; 049 050 /** 051 * Constructs an empty <code>HashBag</code>. 052 */ 053 public HashBag() { 054 super(new HashMap()); 055 } 056 057 /** 058 * Constructs a bag containing all the members of the given collection. 059 * 060 * @param coll a collection to copy into this bag 061 */ 062 public HashBag(Collection coll) { 063 this(); 064 addAll(coll); 065 } 066 067 //----------------------------------------------------------------------- 068 /** 069 * Write the bag out using a custom routine. 070 */ 071 private void writeObject(ObjectOutputStream out) throws IOException { 072 out.defaultWriteObject(); 073 super.doWriteObject(out); 074 } 075 076 /** 077 * Read the bag in using a custom routine. 078 */ 079 private void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException { 080 in.defaultReadObject(); 081 super.doReadObject(new HashMap(), in); 082 } 083 084 }