interfazStack.java

import java.util.EmptyStackException;


/**
 * Stack
 *
 * Interface que representa a un Stack.
 */

public interface interfazStack<E> {

    /**
     * pre:
     * post: item is added to stack
     * will be popped next if no intervening push
     *
     * @param item item to push to the stack.
     */
    public void push(E item);

    /**
     * pre: stack is not empty
     * post: most recently pushed item is removed and returned
     *
     * @return the element in the top of the stack.
     * @throws EmptyStackException If the stack is empty.
     */
    public E pop() throws EmptyStackException;

    /**
     * pre: stack is not empty
     * post: top value (next to be popped) is returned
     *
     * @return the element in the top of the stack.
     * @throws EmptyStackException If the stack is empty.
     */
    public E peek() throws EmptyStackException;

    /**
     * post: returns true if and only if the stack is empty
     *
     * @return True if empty, false otherwise.
     */
    public boolean empty();

    /**
     * post: returns the number of elements in the stack
     *
     * @return The number of elements in the stack.
     */
    public int size();

}