// Robot uses the built-in Color class in java.awt.Color.  (see Java API)
import java.awt.Color;

/**   A Robot is a self-animating object that 
 *    moves (or tries to move) when you switch it on.
 */
public class Robot implements Runnable {

   // fields

   //    parts
   private Thread spirit;        // label for thread that will run run()
   protected Stepper myStepper;  // used for moving forward or backward 

   //    properties/characterisitcs/attributes
   private Color c;

   //    state
   protected boolean  on;            

   // constructor

   public Robot( Stepper s, Color c )
   {
      this.myStepper = s;
      this.c = c;

      this.spirit = new Thread( this );
      this.spirit.start();
   }

   // methods

   /**   switchOn() turns the robot on
    */
   public void switchOn() {
      this.on = true;
   }

   /**   switchOff() turns the robot off
    */
   public void switchOff() {
      this.on = false;
   }

   /**   run() has a while(true) whose body calls act() if the robot
    *    is on, and does nothing otherwise.
    */
   public void run() {
      while( true ) {
         if (on) {
            act();
         }
      }
   }

   /**   This method is called periodically by run() if the robot is on.
    */
   public void act() {
      try {
         // try to step forward
         myStepper.stepForward();
      } catch (CannotStepException e) {
         // if it's not possible, shout for help
         System.out.println( "I'm stuck!  Help me!" );
      }
   }
}