public interface Comparable {

  /**
   * <code>compareTo</code> should return -1 if the current
   * object is "less" than the parameter object, 1 if "greater"
   * or 0 if equal. It is advisable to also implement the 
   * <code>equals()</code> method for your objects so that it
   * consistent with this method.
   *
   * @param obj an <code>Object</code> value
   * @return an <code>int</code> value
   */

  public int compareTo (Object obj);
  
}