Harvest Around Square 4 Robots with Threads

Code

package HarvestAroundSquare4Threads;
import cs1Lib.karel.*;

/** Use four robots to harvest beepers that are positioned
around a square.  Each robot is running in its own thread
and, once started, is independent of the others.
@author Byron Weber Becker
@version 1.0 */
public class HarvestAroundSquare4T extends KarelApplet
{

   public void run()
   {  // Read the specification of the world from a URL.  Then add the
      // world to the applet.  
      World world = new World(this.getDocumentBase(), "HarvestAroundSquare.txt");
      this.add(world);

      // Construct four robots and position them in the world.
      Harvester karel = new Harvester();
      Harvester mary = new Harvester();
      Harvester john = new Harvester();
      Harvester suelynn = new Harvester();
      world.addRobot(karel, 2, 3, World.EAST);
      world.addRobot(mary, 6, 2, World.NORTH);
      world.addRobot(john, 7, 6, World.WEST);
      world.addRobot(suelynn, 3, 7, World.SOUTH);

      // Start each robot.
      new Thread(karel).start();
      new Thread(mary).start();
      new Thread(john).start();
      new Thread(suelynn).start();
   }
}

package HarvestAroundSquare4Threads;
import cs1Lib.karel.*;

/** A robot to pick up a line of beepers, ending in
a wall.  Checks to see if the beeper is actually
present before attempting to pick it up.
@author Byron Weber Becker
@version 1.0 */
public class Harvester extends Robot implements Runnable
{

   public void run()
   {
      while (this.frontIsClear())
      {  this.move();
         if (this.nextToABeeper())
            this.pickBeeper();
      }
      this.turnOff();
   }
}