/**
 * CharNode.java
 * This Class implements a stack of characters
 * 
 * @author Mr J 
 * @version 20050211 
 */
public class CharacterStack
{
  CharNode item;
  CharNode top;
  /**
   * CharacterStack constructor.
   */
  public CharacterStack() { top = null; }
  /**
   * Test for empty stack
   */
  public boolean isEmpty()
  {
    return (top == null);
  }
  /**
   * pop character from stack - check for underflow
   */
  public char pop()
  {
    CharNode temp;	
    if (!isEmpty())
    {
      temp = top;
      top = temp.getNext();
      return temp.getItem();
    }
    else
    {
      return '\0';  // return null char on error
    }
  }
  /**
   * push character on stack.
   */
  public void push(char ch)
  {
    CharNode temp = new CharNode( ch, top);
    top = temp;
  }
}