AbstractQueue


1   /*
2     * JBoss, Home of Professional Open Source
3     * Copyright 2005, JBoss Inc., and individual contributors as indicated
4     * by the @authors tag. See the copyright.txt in the distribution for a
5     * full listing of individual contributors.
6     *
7     * This is free software; you can redistribute it and/or modify it
8     * under the terms of the GNU Lesser General Public License as
9     * published by the Free Software Foundation; either version 2.1 of
10    * the License, or (at your option) any later version.
11    *
12    * This software is distributed in the hope that it will be useful,
13    * but WITHOUT ANY WARRANTY; without even the implied warranty of
14    * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15    * Lesser General Public License for more details.
16    *
17    * You should have received a copy of the GNU Lesser General Public
18    * License along with this software; if not, write to the Free
19    * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
20    * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
21    */
22  package org.jboss.util.collection;
23  
24  import java.util.AbstractCollection  ;
25  
26  /**
27   * An abstract implementation of a Queue.  Sub-classes must provide methods
28   * for <code>addLast(Object)</code> and <code>removeFirst()</code>.
29   *
30   * @version <tt>$Revision: 1958 $</tt>
31   * @author  <a HREF="mailto:jason@planet57.com">Jason Dillon</a>
32   */
33  public abstract class AbstractQueue
34     extends AbstractCollection  
35     implements Queue
36  {
37     /** Default maximum queue size */
38     public static int DEFAULT_MAXIMUM_SIZE = UNLIMITED_MAXIMUM_SIZE;
39  
40     /** Maximum queue size */
41     protected int maximumSize = DEFAULT_MAXIMUM_SIZE;
42  
43     /**
44      * Initializes the AbstractQueue.
45      */
46     protected AbstractQueue() {}
47  
48     /**
49      * Initializes the AbstractQueue.
50      *
51      * @param maxSize    Maximum queue size.
52      *
53      * @exception IllegalArgumentException    Illegal size.
54      */
55     protected AbstractQueue(final int maxSize) {
56        setMaximumSize(maxSize);
57     }
58  
59     /**
60      * Get the maximum size of the queue.
61      *
62      * @return  Maximum queue size or {@link #UNLIMITED_MAXIMUM_SIZE}.
63      */
64     public int getMaximumSize() {
65        return maximumSize;
66     }
67  
68     /**
69      * Set the maximum size of the queue
70      *
71      * @param size    New maximim queue size or {@link #UNLIMITED_MAXIMUM_SIZE}.
72      *
73      * @exception IllegalArgumentException    Illegal size.
74      */
75     public void setMaximumSize(final int size) {
76        if (size < 0 && size != UNLIMITED_MAXIMUM_SIZE)
77           throw new IllegalArgumentException  ("illegal size: " + size);
78  
79        maximumSize = size;
80     }
81  
82     /**
83      * Check if the queue is full.
84      *
85      * @return  True if the queue is full.
86      */
87     public boolean isFull() {
88        if (maximumSize != UNLIMITED_MAXIMUM_SIZE && size() >= maximumSize)
89           return true;
90  
91        return false;
92     }
93  
94     /**
95      * Check if the queue is empty.
96      *
97      * @return True if the queue is empty.
98      */
99     public boolean isEmpty() {
100       if (size() <= 0)
101          return true;
102 
103       return false;
104    }
105 
106    /**
107     * Append and object to the underling list.
108     *
109     * @param obj     Object to enqueue.
110     * @return        True if collection was modified.
111     *
112     * @exception FullCollectionException     The queue is full.
113     */
114    public boolean add(Object   obj) throws FullCollectionException {
115       if (isFull())
116          throw new FullCollectionException();
117 
118       return addLast(obj);
119    }
120 
121    /**
122     * Remove and return the first object in the queue.
123     *
124     * @return  Dequeued object.
125     *
126     * @exception EmptyCollectionException    The queue is empty.
127     */
128    public Object   remove() throws EmptyCollectionException {
129       if (isEmpty())
130          throw new EmptyCollectionException();
131 
132       return removeFirst();
133    }
134 
135    /**
136     * Removes all of the elements from this queue
137     */
138    public void clear() {
139       while (!isEmpty()) {
140          remove();
141       }
142    }
143 
144    /**
145     * Appends the given element to the end of the queue
146     *
147     * @param obj  Object to append
148     * @return     Per Collection.add(), we return a boolean to indicate if
149     *             the object modified the collection.
150     */
151    protected abstract boolean addLast(Object   obj);
152 
153    /**
154     * Remove the first object in the queue
155     *
156     * @return  First object in the queue
157     */
158    protected abstract Object   removeFirst();
159 }
160
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags