objectstack.java

来自「java jdk 1.4的源码」· Java 代码 · 共 252 行

/*
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 1999 The Apache Software Foundation.  All rights 
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
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 * 5. Products derived from this software may not be called "Apache",
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 1999, Lotus
 * Development Corporation., http://www.lotus.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */
package org.apache.xml.utils;

import java.util.EmptyStackException;

/**
 * <meta name="usage" content="internal"/>
 * Implement a stack of simple integers.
 *
 * %OPT%
 * This is currently based on ObjectVector, which permits fast acess but pays a
 * heavy recopying penalty if/when its size is increased. If we expect deep
 * stacks, we should consider a version based on ChunkedObjectVector.
 */
public class ObjectStack extends ObjectVector
{

  /**
   * Default constructor.  Note that the default
   * block size is very small, for small lists.
   */
  public ObjectStack()
  {
    super();
  }

  /**
   * Construct a ObjectVector, using the given block size.
   *
   * @param blocksize Size of block to allocate
   */
  public ObjectStack(int blocksize)
  {
    super(blocksize);
  }

  /**
   * Copy constructor for ObjectStack
   * 
   * @param v ObjectStack to copy
   */
  public ObjectStack (ObjectStack v)
  {
  	super(v);
  }
  
  /**
   * Pushes an item onto the top of this stack.
   *
   * @param   i   the int to be pushed onto this stack.
   * @return  the <code>item</code> argument.
   */
  public Object push(Object i)
  {

    if ((m_firstFree + 1) >= m_mapSize)
    {
      m_mapSize += m_blocksize;

      Object newMap[] = new Object[m_mapSize];

      System.arraycopy(m_map, 0, newMap, 0, m_firstFree + 1);

      m_map = newMap;
    }

    m_map[m_firstFree] = i;

    m_firstFree++;

    return i;
  }

  /**
   * Removes the object at the top of this stack and returns that
   * object as the value of this function.
   *
   * @return     The object at the top of this stack.
   */
  public Object pop()
  {
    Object val = m_map[--m_firstFree];
    m_map[m_firstFree] = null;
    
    return val;
  }

  /**
   * Quickly pops a number of items from the stack.
   */

  public void quickPop(int n)
  {
    m_firstFree -= n;
  }

  /**
   * Looks at the object at the top of this stack without removing it
   * from the stack.
   *
   * @return     the object at the top of this stack.
   * @throws  EmptyStackException  if this stack is empty.
   */
  public Object peek()
  {
    try {
      return m_map[m_firstFree - 1];
    }
    catch (ArrayIndexOutOfBoundsException e)
    {
      throw new EmptyStackException();
    }
  }

  /**
   * Looks at the object at the position the stack counting down n items.
   *
   * @param n The number of items down, indexed from zero.
   * @return     the object at n items down.
   * @throws  EmptyStackException  if this stack is empty.
   */
  public Object peek(int n)
  {
    try {
      return m_map[m_firstFree-(1+n)];
    }
    catch (ArrayIndexOutOfBoundsException e)
    {
      throw new EmptyStackException();
    }
  }

  /**
   * Sets an object at a the top of the statck
   *
   *
   * @param val object to set at the top
   * @throws  EmptyStackException  if this stack is empty.
   */
  public void setTop(Object val)
  {
    try {
      m_map[m_firstFree - 1] = val;
    }
    catch (ArrayIndexOutOfBoundsException e)
    {
      throw new EmptyStackException();
    }
  }

  /**
   * Tests if this stack is empty.
   *
   * @return  <code>true</code> if this stack is empty;
   *          <code>false</code> otherwise.
   * @since   JDK1.0
   */
  public boolean empty()
  {
    return m_firstFree == 0;
  }

  /**
   * Returns where an object is on this stack.
   *
   * @param   o   the desired object.
   * @return  the distance from the top of the stack where the object is]
   *          located; the return value <code>-1</code> indicates that the
   *          object is not on the stack.
   * @since   JDK1.0
   */
  public int search(Object o)
  {

    int i = lastIndexOf(o);

    if (i >= 0)
    {
      return size() - i;
    }

    return -1;
  }

  /**
   * Returns clone of current ObjectStack
   * 
   * @return clone of current ObjectStack
   */
  public Object clone()
    throws CloneNotSupportedException
  {
  	return (ObjectStack) super.clone();
  }  
  
}