====== طراحی پشته ======
<code java>


     /** 
      * Interface for a stack: a collection of objects that are inserted
      * and removed according to the last-in first-out principle.
      * 
      * @author Roberto Tamassia
      * @author Michael Goodrich
      * @see EmptyStackException
      */

    public interface Stack {
     /**
      * Return the number of elements in the stack.
      * @return number of elements in the stack. 
      */
      public int size();
     /** 
      * Return whether the stack is empty.
      * @return true if the stack is empty, false otherwise. 
      */
      public boolean isEmpty();
     /** 
      * Inspect the element at the top of the stack.
      * @return top element in the stack.  
      * @exception EmptyStackException if the stack is empty. 
      */
      public Object top() 
        throws EmptyStackException;  
     /**
      * Insert an element at the top of the stack.
      * @param element element to be inserted.
      */
      public void push (Object element); 
     /** 
      * Remove the top element from the stack.
      * @return element removed.
      * @exception EmptyStackException if the stack is empty.
      */
      public Object pop()
        throws EmptyStackException; 
    }
</code>