ArrayStack.java

package StackQueueAlgo;

public class ArrayStack implements Stack {
	public  static final int CAPACITY = 10;
	private static int _capacity;
	private static Object _S[];
	private static int _top = -1;
	
	public ArrayStack() {
		this(CAPACITY);
	} 
	public ArrayStack(int cap) {
		_capacity = cap;
		_S = new Object[_capacity];
	}	 
	public int size() { 
		return (_top + 1);
	}
	public boolean isEmpty() { 
		return (_top < 0);
	}
	public Object top() {
		try {
			if (isEmpty())
				throw new StackKosongException("Stack is empty.");
		} catch (Exception e) { 
			e.printStackTrace(); 
		} 
		return _S[_top];
	}
	public void push(Object element) {
		if (size() == _capacity) {
			try {
				throw new StackPenuhException("Stack overflow.");
			} catch (Exception e) { 
				e.printStackTrace();
			}
		}
		_S[++_top] = element;
	}
	public Object pop() {
		Object elem = null;
		try { 
			if (isEmpty()) 
				throw new StackKosongException("Stack is empty."); 
			elem = _S[_top];
			_S[_top--] = null;
		} catch (Exception e) { 
			e.printStackTrace(); 
		} 
		return elem; 
	}

	public static void display() {
		 if (_top > _capacity) {
			 System.out.println(">> Elemen di antrian:");
			 for (int i = _top; i <= _capacity; i++)
				 System.out.println(_S[i]);
		 }
	 }
	
	/* demo goes here */
	public static void main(String[] args) {  
		ArrayStack q = new ArrayStack( );

        	try {
			q.push(1);
			q.push(2);
			q.push(3);
			q.push(4);
			q.pop();	// remove 1st element from stack
			q.push(5);
			q.push(6);
			q.pop();	// remove 2nd element from stack
		}
		catch( UnderflowException e ) { System.out.println( "Unexpected overflow" ); }
        
		System.out.println("Final result:");
		while( !q.isEmpty() )
			System.out.println( q.pop() ); 
	}
}

interface Stack {  
	public int size();			// return: num of elements in the stack 		
	public boolean isEmpty();		// return: true, if stack is empty. otherwise false
	public Object top()
		throws StackKosongException;    // return: top element in the stack
	public void push (Object element);     // push an element to stack
	public Object pop()
		throws StackKosongException;	// return and remove top element in the stack
}

@SuppressWarnings("serial") 
class StackKosongException extends RuntimeException {
	public StackKosongException( String message )
    {
        super( message );
    }
}

@SuppressWarnings("serial")
class StackPenuhException extends RuntimeException {
	public StackPenuhException ( String message ) {
		super ( message );
	}
}