package stacks;


public class ArrayStack<E> implements Stack<E>{
	private int capacity; //The actual capacity of the stack array
	public static final int CAPACITY = 100; //default array capacity
	private E s[]; //Generic array used to implement the stack
	private int top = -1; //index for the top of the stack
	
	public ArrayStack(){
		this(CAPACITY);
	}
	
	public ArrayStack(int cap){
		capacity=cap;
		s=(E[]) new Object[capacity];//compiler may give a warning, but this is ok
		//Used instead of S=new E[cap];Since can't create a new array using parameterised type
	}
	
	public int size(){
		return (top+1);
	}
	 
	public boolean isEmpty(){
		return (top<0);
	}
	
	public void push(E element) throws FullStackException {
		if (size()==capacity)
			throw new FullStackException("Stack is full.");
		s[++top]=element;
	}
	
	public E top() throws EmptyStackException{
		if (isEmpty())
			throw new EmptyStackException("Stack is empty.");
		return s[top];
	}
	
	public E pop() throws EmptyStackException {
		E element;
		if (isEmpty())
			throw new EmptyStackException("Stack is empty");
		element = s[top];
		s[top--]=null; //dereference S[top] for garbage collection
		return element;
	}
	
	public String toString(){
		String st;
		st="[";
		if (size()>0) st+=s[0];
		if (size()>1)
			for (int i=1;i<=size()-1;i++){
				st+=","+s[i];
			}
		return st + "]";
			}
	
	// Prints status information about a recent operation and the stack
	public void status(String op, Object element){
		System.out.print("------> " + op); //print this operation
		System.out.println(", returns " + element); //what was returned
		System.out.print("result: size = " + size() + ", isEmpty= " +isEmpty());
		System.out.println(", stack: " + this); //contents of the stack
	}
	
	
	}