Installing an External Library in BlueJ with an external .jar file

Make a New Project in BlueJ

Select Preferences (In MacOS it is under the 'BlueJ' menu,in Windows it is under 'Tools' )

Click the Libraries Tab

Press the Add File button

Select the kareljrobot.jar file or other .jar file you downloaded, press the Open button

It will tell you to restart the Virtual Machine, press the Okay button

Under the Tools menu select Reset Java Virtual Machine (or press Ctrl-Shift-R) Sometimes it is best to simply Quit and relaunch BlueJ.

To test the APLU Turtle Library jturtle-0.1.1.jar, try this example program:

import ch.aplu.turtle.*;
import java.awt.Color;
/**
 * 
 * @author (Your Name)
 * @version September 0, 2024
 */
public class MyPicture {
 
	public static void main(String[] args) {		
 
        Turtle hexter = new Turtle(Color.GREEN);
        hexter.setPos(100,-50);
 
 
        for (int i=0; i< 6; i++) {
        	hexter.forward(100);
        	hexter.right(-60);
        }
        hexter.setPos(0,0);
        hexter.setFillColor(Color.BLUE);
	    hexter.fill();
 
        Turtle t = new Turtle(hexter); 
        t.setColor(Color.RED);
		t.setPos(-200, 180);
	    t.hideTurtle().label( "by My name"); 	
 
	}
 
}

To test our the kareljrobot.jarinstallation, make a new class RobotRunner to test it out:

  import kareltherobot.*;
  public class RobotRunner implements Directions
  {
	public static void main(String[] args) 
	{
		World.setDelay(150);
		World.placeBeepers(4, 3, 2);
		World.setVisible();
	}
  }