import java.util.*;

public class Stack implements StackADT {
	private LinkedList<Object> stack;

	Stack () {
		this.stack = new LinkedList<Object>();
	}

	public boolean empty() {
		return (this.size() == 0);
	}

	public int size() {
		return this.stack.size();
	}

	public Object peek() throws EmptyStackException {
		if(!this.empty()) {
			return this.stack.getLast();
		} else {
			throw new EmptyStackException();
		}
	}

	public Object pop() throws EmptyStackException {
		if(!this.empty()) {
			return this.stack.removeLast();
		} else {
			throw new EmptyStackException();
		}
	}

	public void push(Object item) {
		this.stack.add(item);
	}


}