/*
 * Single-linked implementation
 * with count and private class List
 */

package stackl;

//stack implemented as list
//the topmost element of stack is head
//the body of the stack is tail

/**
 *
 * @author suchenek
 */
public class Stack
{    
    private class List
    {
        protected Object head;
        protected List tail;
    }
    private List stack; //so that count does not occur in substacks
    private int count;
    
    public void makenull()
    {
        stack = null;
        count = 0;
    }

    public void push(Object newItem)
    {
        List temp = new List();
        temp.head = newItem;
        temp.tail = this.stack;
        this.stack = temp;
        count++;
    }
    
    public Object pop()
    {
        if (stack == null) return null;
        Object toReturn;
        toReturn = stack.head;
        stack = stack.tail;
        count--;
        return toReturn;
    }
    public int size()
    {
          return count;          
    }
      
    public boolean isEmpty()
    {
          return stack == null;
    }

    public int Length()
    {
          return 0;
          
    }
}