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();
	}
  }