package rebelsky.linear;

/**
 * An implementation of stacks using arrays.  Currently incomplete,
 * as it fails when the array fills.
 *
 * @author Samuel A. Rebelsky
 * @version 1.0 of October 2004.
 */
public class ArrayBasedStack
	implements Stack
{
// +--------+--------------------------------------------------
// | Fields |
// +--------+

	/** The index of the "last" thing. */
	int lastThing;
	
	/** The stuff actually in the stack. */
	Object[] contents;

// +--------------+--------------------------------------------
// | Constructors |
// +--------------+
	
	public ArrayBasedStack()
	{
		this.lastThing = -1;
		this.contents = new Object[3];
	} // ArrayBasedStack()

// +---------+-------------------------------------------------
// | Methods |
// +---------+

	public void put(Object addMe)
	{
		this.contents[this.lastThing+1] = addMe;
		this.lastThing += 1;
	} // put(Object)

	public Object get()
	{
		Object returnMe = this.contents[this.lastThing];
		this.contents[this.lastThing] = null; // Actually remove it.
		this.lastThing -= 1;
		return returnMe;
	} // get()

	public Object peek()
	{
		return this.contents[this.lastThing];
	} // peek()

	public boolean isEmpty()
	{
		return this.lastThing == -1;
	} // isEmpty()

} // ArrayBasedStack()