| /* Stack.java - Class that provides a Last In First Out (LIFO) |
| datatype, known more commonly as a Stack |
| Copyright (C) 1998, 1999, 2001, 2005 Free Software Foundation, Inc. |
| |
| This file is part of GNU Classpath. |
| |
| GNU Classpath is free software; you can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2, or (at your option) |
| any later version. |
| |
| GNU Classpath is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received a copy of the GNU General Public License |
| along with GNU Classpath; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA |
| 02110-1301 USA. |
| |
| Linking this library statically or dynamically with other modules is |
| making a combined work based on this library. Thus, the terms and |
| conditions of the GNU General Public License cover the whole |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package java.util; |
| |
| /* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3 |
| * "The Java Language Specification", ISBN 0-201-63451-1 |
| * plus online API docs for JDK 1.2 beta from http://www.javasoft.com. |
| * Status: Believed complete and correct |
| |
| /** |
| * Stack provides a Last In First Out (LIFO) data type, commonly known |
| * as a Stack. Stack itself extends Vector and provides the additional |
| * methods for stack manipulation (push, pop, peek). You can also seek for |
| * the 1-based position of an element on the stack. |
| * |
| * @author Warren Levy (warrenl@cygnus.com) |
| * @author Eric Blake (ebb9@email.byu.edu) |
| * @see List |
| * @see AbstractList |
| * @see LinkedList |
| * @since 1.0 |
| * @status updated to 1.4 |
| */ |
| public class Stack extends Vector |
| { |
| // We could use Vector methods internally for the following methods, |
| // but have used Vector fields directly for efficiency (i.e. this |
| // often reduces out duplicate bounds checking). |
| |
| /** |
| * Compatible with JDK 1.0+. |
| */ |
| private static final long serialVersionUID = 1224463164541339165L; |
| |
| /** |
| * This constructor creates a new Stack, initially empty |
| */ |
| public Stack() |
| { |
| } |
| |
| /** |
| * Pushes an Object onto the top of the stack. This method is effectively |
| * the same as addElement(item). |
| * |
| * @param item the Object to push onto the stack |
| * @return the Object pushed onto the stack |
| * @see Vector#addElement(Object) |
| */ |
| public Object push(Object item) |
| { |
| // When growing the Stack, use the Vector routines in case more |
| // memory is needed. |
| // Note: spec indicates that this method *always* returns obj passed in! |
| |
| addElement(item); |
| return item; |
| } |
| |
| /** |
| * Pops an item from the stack and returns it. The item popped is |
| * removed from the Stack. |
| * |
| * @return the Object popped from the stack |
| * @throws EmptyStackException if the stack is empty |
| */ |
| public synchronized Object pop() |
| { |
| if (elementCount == 0) |
| throw new EmptyStackException(); |
| |
| modCount++; |
| Object obj = elementData[--elementCount]; |
| |
| // Set topmost element to null to assist the gc in cleanup. |
| elementData[elementCount] = null; |
| return obj; |
| } |
| |
| /** |
| * Returns the top Object on the stack without removing it. |
| * |
| * @return the top Object on the stack |
| * @throws EmptyStackException if the stack is empty |
| */ |
| public synchronized Object peek() |
| { |
| if (elementCount == 0) |
| throw new EmptyStackException(); |
| |
| return elementData[elementCount - 1]; |
| } |
| |
| /** |
| * Tests if the stack is empty. |
| * |
| * @return true if the stack contains no items, false otherwise |
| */ |
| public synchronized boolean empty() |
| { |
| return elementCount == 0; |
| } |
| |
| /** |
| * Returns the position of an Object on the stack, with the top |
| * most Object being at position 1, and each Object deeper in the |
| * stack at depth + 1. |
| * |
| * @param o The object to search for |
| * @return The 1 based depth of the Object, or -1 if the Object |
| * is not on the stack |
| */ |
| public synchronized int search(Object o) |
| { |
| int i = elementCount; |
| while (--i >= 0) |
| if (equals(o, elementData[i])) |
| return elementCount - i; |
| return -1; |
| } |
| } |