public class Tail implements Sensor 
{
   /**   returns true if the sensor is currently sensing something
    *    otherwise returns false.
    */
   public boolean sensesSomething() {
      // do whatever Tails do to sense something.
      // ...
      // if tail does sense something, we should say
      // return true;
      // otherwise, say return false;

      // just return false for now because we *must* return
      // some boolean.
      return false;
   }
}