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/* ====================================================================
* The Apache Software License, Version 1.1
*
* Copyright (c) 2001-2004 The Apache Software Foundation. All rights
* reserved.
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* 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.
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* any, must include the following acknowledgement:
* "This product includes software developed by the
* Apache Software Foundation (http://www.apache.org/)."
* Alternately, this acknowledgement may appear in the software itself,
* if and wherever such third-party acknowledgements normally appear.
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* SUCH DAMAGE.
* ====================================================================
*
* This software consists of voluntary contributions made by many
* individuals on behalf of the Apache Software Foundation. For more
* information on the Apache Software Foundation, please see
* ArrayList instead of a Vector, so it is not
* synchronized to protect against multi-threaded access. The implementation
* is therefore operates faster in environments where you do not need to
* worry about multiple thread contention.
*
* The removal order of an ArrayStack is based on insertion
* order: The most recently added element is removed first. The iteration
* order is not the same as the removal order. The iterator returns
* elements from the bottom up, whereas the {@link #remove()} method removes
* them from the top down.
*
* Unlike Stack, ArrayStack accepts null entries.
*
* @see java.util.Stack
* @since Commons Collections 1.0
* @version $Revision: 1.16 $ $Date: 2004/01/14 21:43:03 $
*
* @author Craig R. McClanahan
* @author Paul Jack
* @author Stephen Colebourne
*/
public class ArrayStack extends ArrayList implements Buffer {
/** Ensure serialization compatibility */
private static final long serialVersionUID = 2130079159931574599L;
/**
* Constructs a new empty ArrayStack. The initial size
* is controlled by ArrayList and is currently 10.
*/
public ArrayStack() {
super();
}
/**
* Constructs a new empty ArrayStack with an initial size.
*
* @param initialSize the initial size to use
* @throws IllegalArgumentException if the specified initial size
* is negative
*/
public ArrayStack(int initialSize) {
super(initialSize);
}
/**
* Return true if this stack is currently empty.
*
* This method exists for compatibility with java.util.Stack.
* New users of this class should use isEmpty instead.
*
* @return true if the stack is currently empty
*/
public boolean empty() {
return isEmpty();
}
/**
* Returns the top item off of this stack without removing it.
*
* @return the top item on the stack
* @throws EmptyStackException if the stack is empty
*/
public Object peek() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
} else {
return get(n - 1);
}
}
/**
* Returns the n'th item down (zero-relative) from the top of this
* stack without removing it.
*
* @param n the number of items down to go
* @return the n'th item on the stack, zero relative
* @throws EmptyStackException if there are not enough items on the
* stack to satisfy this request
*/
public Object peek(int n) throws EmptyStackException {
int m = (size() - n) - 1;
if (m < 0) {
throw new EmptyStackException();
} else {
return get(m);
}
}
/**
* Pops the top item off of this stack and return it.
*
* @return the top item on the stack
* @throws EmptyStackException if the stack is empty
*/
public Object pop() throws EmptyStackException {
int n = size();
if (n <= 0) {
throw new EmptyStackException();
} else {
return remove(n - 1);
}
}
/**
* Pushes a new item onto the top of this stack. The pushed item is also
* returned. This is equivalent to calling add.
*
* @param item the item to be added
* @return the item just pushed
*/
public Object push(Object item) {
add(item);
return item;
}
/**
* Returns the one-based position of the distance from the top that the
* specified object exists on this stack, where the top-most element is
* considered to be at distance 1. If the object is not
* present on the stack, return -1 instead. The
* equals() method is used to compare to the items
* in this stack.
*
* @param object the object to be searched for
* @return the 1-based depth into the stack of the object, or -1 if not found
*/
public int search(Object object) {
int i = size() - 1; // Current index
int n = 1; // Current distance
while (i >= 0) {
Object current = get(i);
if ((object == null && current == null) ||
(object != null && object.equals(current))) {
return n;
}
i--;
n++;
}
return -1;
}
/**
* Returns the element on the top of the stack.
*
* @return the element on the top of the stack
* @throws BufferUnderflowException if the stack is empty
*/
public Object get() {
int size = size();
if (size == 0) {
throw new BufferUnderflowException();
}
return get(size - 1);
}
/**
* Removes the element on the top of the stack.
*
* @return the removed element
* @throws BufferUnderflowException if the stack is empty
*/
public Object remove() {
int size = size();
if (size == 0) {
throw new BufferUnderflowException();
}
return remove(size - 1);
}
}