1 /* Stack.java - Class that provides a Last In First Out (LIFO)
2 datatype, known more commonly as a Stack
3 Copyright (C) 1998, 1999, 2001, 2004, 2005
4 Free Software Foundation, Inc.
6 This file is part of GNU Classpath.
8 GNU Classpath is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2, or (at your option)
13 GNU Classpath is distributed in the hope that it will be useful, but
14 WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GNU Classpath; see the file COPYING. If not, write to the
20 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
23 Linking this library statically or dynamically with other modules is
24 making a combined work based on this library. Thus, the terms and
25 conditions of the GNU General Public License cover the whole
28 As a special exception, the copyright holders of this library give you
29 permission to link this library with independent modules to produce an
30 executable, regardless of the license terms of these independent
31 modules, and to copy and distribute the resulting executable under
32 terms of your choice, provided that you also meet, for each linked
33 independent module, the terms and conditions of the license of that
34 module. An independent module is a module which is not derived from
35 or based on this library. If you modify this library, you may extend
36 this exception to your version of the library, but you are not
37 obligated to do so. If you do not wish to do so, delete this
38 exception statement from your version. */
43 /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
44 * "The Java Language Specification", ISBN 0-201-63451-1
45 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
46 * Status: Believed complete and correct
49 * Stack provides a Last In First Out (LIFO) data type, commonly known
50 * as a Stack. Stack itself extends Vector and provides the additional
51 * methods for stack manipulation (push, pop, peek). You can also seek for
52 * the 1-based position of an element on the stack.
54 * @author Warren Levy (warrenl@cygnus.com)
55 * @author Eric Blake (ebb9@email.byu.edu)
60 * @status updated to 1.4
62 public class Stack/*<T>*/ extends Vector/*<T>*/
64 // We could use Vector methods internally for the following methods,
65 // but have used Vector fields directly for efficiency (i.e. this
66 // often reduces out duplicate bounds checking).
69 * Compatible with JDK 1.0+.
71 private static final long serialVersionUID = 1224463164541339165L;
74 * This constructor creates a new Stack, initially empty
82 * Pushes an Object onto the top of the stack. This method is effectively
83 * the same as addElement(item).
85 * @param item the Object to push onto the stack
86 * @return the Object pushed onto the stack
87 * @see Vector#addElement(Object)
89 public Object push(Object item)
91 // When growing the Stack, use the Vector routines in case more
93 // Note: spec indicates that this method *always* returns obj passed in!
100 * Pops an item from the stack and returns it. The item popped is
101 * removed from the Stack.
103 * @return the Object popped from the stack
104 * @throws EmptyStackException if the stack is empty
106 //@SuppressWarnings("unchecked")
107 public synchronized Object pop()
110 throw new /*EmptyStack*/Exception("EmptyStackException");
112 Object obj = array[--size];
114 // Set topmost element to null to assist the gc in cleanup.
120 * Returns the top Object on the stack without removing it.
122 * @return the top Object on the stack
123 * @throws EmptyStackException if the stack is empty
125 //@SuppressWarnings("unchecked")
126 public synchronized Object peek()
129 throw new /*EmptyStack*/Exception("EmptyStackException");
131 return array[size - 1];
135 * Tests if the stack is empty.
137 * @return true if the stack contains no items, false otherwise
139 public synchronized boolean empty()
145 * Returns the position of an Object on the stack, with the top
146 * most Object being at position 1, and each Object deeper in the
147 * stack at depth + 1.
149 * @param o The object to search for
150 * @return The 1 based depth of the Object, or -1 if the Object
151 * is not on the stack
153 public synchronized int search(Object o)
157 if (o.equals(array[i]))