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/*******************************************************************************
* Copyright (c) 2007 IBM Corporation and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*
*******************************************************************************/
package org.eclipse.jst.jsp.core.internal.java;
import java.util.HashMap;
import java.util.Map;
import java.util.Stack;
/**
* @author nitin
*
*/
class StackMap {
private Map fInternalMap = null;
public StackMap() {
fInternalMap = new HashMap();
}
/**
* Removes all mappings from this StackMap
*/
public void clear() {
fInternalMap.clear();
}
/**
* Returns the most recently pushed value to which this map maps the
* specified key. Returns <tt>null</tt> if the map contains no mapping
* for this key.
*
* @param key
* key whose associated value is to be returned.
* @return the most recently put value to which this map maps the
* specified key, or <tt>null</tt> if the map contains no
* mapping for this key.
*/
public Object peek(Object key) {
Stack stack = (Stack) fInternalMap.get(key);
if (stack != null) {
Object o = stack.peek();
if (stack.isEmpty()) {
fInternalMap.remove(key);
}
return o;
}
return null;
}
/**
* Associates the specified value with the specified key in this map. If
* the map previously contained a mapping for this key, the old value is
* pushed onto the top of this key's private stack.
*
* @param key
* key with which the specified value is to be associated.
* @param value
* value to be associated with the specified key.
* @return newest value associated with specified key
*
* @throws UnsupportedOperationException
* if the <tt>put</tt> operation is not supported by this
* StackMap.
* @throws ClassCastException
* if the class of the specified key or value prevents it from
* being stored in this StackMap.
* @throws IllegalArgumentException
* if some aspect of this key or value prevents it from being
* stored in this StackMap.
* @throws NullPointerException,
* as this map does not permit <tt>null</tt> keys or values
*/
public Object push(Object key, Object value) {
Stack stack = (Stack) fInternalMap.get(key);
if (stack == null) {
stack = new Stack();
fInternalMap.put(key, stack);
}
Object o = stack.push(value);
return o;
}
/**
* Removes the most-recent mapping for this key from this StackMap if it
* is present.
*
* <p>
* Returns the value to which the map previously associated the key, or
* <tt>null</tt> if the map contained no mapping for this key. The map
* will not contain a mapping for the specified key once the call returns.
*
* @param key
* key whose stack is to be popped
* @return most-recently pushed value associated with specified key, or
* <tt>null</tt> if there was no mapping for key.
*
* @throws ClassCastException
* if the key is of an inappropriate type for this map.
* @throws NullPointerException
* if the key is <tt>null</tt> as this class does not permit
* <tt>null</tt> keys
*/
public Object pop(Object key) {
Stack stack = (Stack) fInternalMap.get(key);
if (stack != null) {
Object o = stack.pop();
if (stack.isEmpty()) {
fInternalMap.remove(key);
}
return o;
}
return null;
}
}
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