package eg.edu.alexu.csd.datastructure.stack;

public class Stack implements IStack {
		int capacity = 2;
		Object[] stack = new Object[capacity];
		int top = 0;

		public int size() {
			return top;
		}

		public void push(Object element) {
			if (size() == capacity)
				expand();

			stack[top] = element;
			top++;

		}

		private void expand() {
			int length = size();
			Object newstack[] = new Object[capacity * 2];
			System.arraycopy(stack, 0, newstack, 0, length);
			stack = newstack;
			capacity *= 2;
		}

		public Object pop() {
			if (isEmpty()) {
				System.out.println("Stack is Empty!");
				return null;
			} else {
				Object data = stack[top - 1];
				stack[top - 1] = 0;
				top--;
				return data;
			}
		}

		public Object peek() {
			if(isEmpty()) {
				return null;
			}
			else {
			Object data = stack[top - 1];
			top--;
			return data;
			}
		}

		public boolean isEmpty() {
			if (size() == 0)
				return true;
			else
				return false;
		}

		public void show() {
			for (Object n : stack) {
				System.out.println( n);

			}

		}
	}