mystack.java

stacktrain is impletemnt by hava

public class MyStack
{
	/**
	 *  Creates a new stack that can hold 1000 elements
	 *
	 */
	Object[] mystack;
	int Capacity = 0;
	int max = 1000;
	int size;

	public MyStack ( )
	{
		mystack = new Object [max];

	}

	/**
	 *
	 * @param initialSize The maximum number of elements to store in the stack
	 */
	public MyStack ( int initialSize )
	{
		mystack = new Object [initialSize];
		size = initialSize;
	}

	/**
	 *  Remove all elements from the stack
	 *
	 */
	public void makeEmpty ()
	{
		for (int i=0; i < mystack.length; i++)
		{
			pop();
		}

	}

	/**
	 * @return is the stack empty?
	 */
	public boolean isEmpty ()
	{
		if (Capacity == 0)
		return true;

		else
		return false;

	}

	/**
	 * @return the number of elements in the stack
	 */
	public int	size ()
	{
		return Capacity;
	}

	/**
	 * Returns the top element on the stack and removes it.
	 * @throws MyStackEmptyException
	 * @return the top element on the stack
	 */
	public Object pop ( ) throws MyStackEmptyException
	{
		Object temp=null;
        //System.out.println("before pop: "+ Capacity);

        if (Capacity == 0)
		{
			throw new MyStackEmptyException();

		}
		else


		{
			temp = mystack[Capacity - 1];

		mystack[Capacity - 1] = null;
		Capacity--;
	    }
		return temp;
	}

	/**
	 * This method returns the top element without removing it from
	 * the stack.
	 * @throws MyStackEmptyException
	 * @return the top element on the stack
	 */
	public Object top ( ) throws MyStackEmptyException
	{
		if (Capacity == 0)
		throw new MyStackEmptyException();
		return mystack[Capacity - 1];

	}

	/**
	 * Push a new element onto the Stack
	 * @throws MyStackFullException
	 */
	public void push ( Object o ) throws MyStackFullException
	{
		//System.out.println("before pop: "+ Capacity);
		if (size == 0)
		{
		   size = max;
	     }
		if (Capacity >= size)
		 {
			 throw new MyStackFullException();
	     }
		else
		{
		 mystack[Capacity]= o;
		 Capacity++;
	    }

	}

}