package example2;

public class Stack {

	// The maximum possible size of a stack.
	public static final int MaxSize = 100;

	// The array index of the last active element
	// in the stack. A value of -1 means the stack
	// is currently empty.
	private int top = -1;
	
	// The stack elements, stored in an array.
	private Object[] store = new Object[MaxSize];
	
	// Number of all pushes (collectively)
	// done to all stacks.
	private static int totalNumberOfPushes = 0;
	
	// Add a new element at the top of the stack
	// (if there’s space left).
	public void push (Object newItem) {
		if (top < MaxSize -1) {
			top++;
			store[top]= newItem;
			totalNumberOfPushes++;
		} else {
		System.err.println ("Sorry, stack full.");
		}
	}

	// Remove the top element of the stack and return
	// it; check that the stack has elements in it!
	public Object pop () {
		Object ans = "";
		if (top >= 0) {
			ans = store[top];
			top--;
		} else {
			System.err.println ("Sorry, stack empty.");
		}
		return ans;
	}

	// Return the number of elements that are 
	// currently in the stack.
	public int size() {
		return top+1;
	}

	// Return the total number of pushes
	// done to all stacks (collectively).
	public static int getNumberOfPushes () {
		return totalNumberOfPushes;
	}

	// Print the stack from top to bottom.
	// (not a standard function of stacks!)
	public void print() {
		int i;
		for (i=top; i>=0; i--) {
			System.out.println(store[i]);
		}
	}

}