001 /**
002 * ========================================
003 * JCommon : a free Java report library
004 * ========================================
005 *
006 * Project Info: http://www.jfree.org/jcommon/
007 *
008 * (C) Copyright 2000-2006, by Object Refinery Limited and Contributors.
009 *
010 * This library is free software; you can redistribute it and/or modify it under the terms
011 * of the GNU Lesser General Public License as published by the Free Software Foundation;
012 * either version 2.1 of the License, or (at your option) any later version.
013 *
014 * This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
015 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
016 * See the GNU Lesser General Public License for more details.
017 *
018 * You should have received a copy of the GNU Lesser General Public License along with this
019 * library; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
020 * Boston, MA 02111-1307, USA.
021 *
022 * [Java is a trademark or registered trademark of Sun Microsystems, Inc.
023 * in the United States and other countries.]
024 *
025 * ------------
026 * $Id: FastStack.java,v 1.3 2008/09/10 09:22:05 mungady Exp $
027 * ------------
028 * (C) Copyright 2002-2006, by Object Refinery Limited.
029 */
030
031 package org.jfree.util;
032
033 import java.io.Serializable;
034 import java.util.Arrays;
035 import java.util.EmptyStackException;
036
037 /**
038 * A very simple unsynchronized stack. This one is faster than the
039 * java.util-Version.
040 *
041 * @author Thomas Morgner
042 */
043 public final class FastStack implements Serializable, Cloneable {
044 private Object[] contents;
045 private int size;
046 private int initialSize;
047
048 /**
049 * Creates a new empty stack.
050 */
051 public FastStack() {
052 this.initialSize = 10;
053 }
054
055 /**
056 * Creates a new empty stack with the specified initial storage size.
057 *
058 * @param size the initial storage elements.
059 */
060 public FastStack(int size) {
061 this.initialSize = Math.max(1, size);
062 }
063
064 /**
065 * Returns <code>true</code> if the stack is empty, and <code>false</code>
066 * otherwise.
067 *
068 * @return A boolean.
069 */
070 public boolean isEmpty() {
071 return this.size == 0;
072 }
073
074 /**
075 * Returns the number of elements in the stack.
076 *
077 * @return The element count.
078 */
079 public int size() {
080 return this.size;
081 }
082
083 /**
084 * Pushes an object onto the stack.
085 *
086 * @param o the object.
087 */
088 public void push(Object o) {
089 if (this.contents == null) {
090 this.contents = new Object[this.initialSize];
091 this.contents[0] = o;
092 this.size = 1;
093 return;
094 }
095
096 final int oldSize = this.size;
097 this.size += 1;
098 if (this.contents.length == this.size) {
099 // grow ..
100 final Object[] newContents = new Object[this.size
101 + this.initialSize];
102 System.arraycopy(this.contents, 0, newContents, 0, this.size);
103 this.contents = newContents;
104 }
105 this.contents[oldSize] = o;
106 }
107
108 /**
109 * Returns the object at the top of the stack without removing it.
110 *
111 * @return The object at the top of the stack.
112 */
113 public Object peek() {
114 if (this.size == 0) {
115 throw new EmptyStackException();
116 }
117 return this.contents[this.size - 1];
118 }
119
120 /**
121 * Removes and returns the object from the top of the stack.
122 *
123 * @return The object.
124 */
125 public Object pop() {
126 if (this.size == 0) {
127 throw new EmptyStackException();
128 }
129 this.size -= 1;
130 final Object retval = this.contents[this.size];
131 this.contents[this.size] = null;
132 return retval;
133 }
134
135 /**
136 * Returns a clone of the stack.
137 *
138 * @return A clone.
139 */
140 public Object clone() {
141 try {
142 FastStack stack = (FastStack) super.clone();
143 if (this.contents != null) {
144 stack.contents = (Object[]) this.contents.clone();
145 }
146 return stack;
147 }
148 catch (CloneNotSupportedException cne) {
149 throw new IllegalStateException("Clone not supported? Why?");
150 }
151 }
152
153 /**
154 * Clears the stack.
155 */
156 public void clear() {
157 this.size = 0;
158 if (this.contents != null) {
159 Arrays.fill(this.contents, null);
160 }
161 }
162
163 /**
164 * Returns the item at the specified slot in the stack.
165 *
166 * @param index the index.
167 *
168 * @return The item.
169 */
170 public Object get(final int index) {
171 if (index >= this.size) {
172 throw new IndexOutOfBoundsException();
173 }
174 return this.contents[index];
175 }
176 }