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/*
* ArrayListStack.java
* Author: [email protected]
* Created on June 21, 2002, 3:42 PM
*
*/
package com.sun.jts.pi;
import java.util.ArrayList;
/**
* The ArrayListStack class represents a last-in-first-out
* (LIFO) stack of objects. It encapsulates class ArrayList with four
* operations that allow a list to be treated as a stack. The usual
* push and pop operations are provided, as well as a
* method to peek at the top item on the stack, and a method to test
* for whether the stack is empty
*
* When a stack is first created, it contains no items.
* @author Darpan Dinker, $Author: tcfujii $
* @version $Revision: 1.3 $ on $Date: 2005/12/25 04:12:09 $
*/
public class ArrayListStack {
private int curIndex;
private ArrayList list;
/** Creates a stack with the given initial size */
public ArrayListStack(int size) {
curIndex = 0;
list = new ArrayList(size);
}
/** Creates a stack with a default size */
public ArrayListStack() {
this(20);
}
/**
* Provides the current size of the stack.
* @return int return the current size.
*/
public int size() {
return curIndex;
}
/**
* Pushes an item onto the top of this stack. This method will internally
* add elements to the ArrayList if the stack is full.
* @param obj the object to be pushed onto this stack.
* @see java.util.ArrayList#add
*/
public void push(Object obj) {
list.add(curIndex, obj);
curIndex += 1;
}
/**
* 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 (the last item
* of the ArrayList object). Null if stack is empty.
*/
public Object pop() {
if (curIndex > 0) {
curIndex -= 1;
return list.remove(curIndex);
}
return null;
}
/**
* Tests if this stack is empty.
* @return true if and only if this stack contains
* no items; false otherwise.
*/
public boolean empty() {
return curIndex == 0;
}
/**
* 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 (the last item
* of the ArrayList object). Null if stack is empty.
*/
public Object peek() {
Object top = null;
if (curIndex > 0) {
top = list.get(curIndex - 1);
}
return top;
}
}