How to fix a NullPointerException error when running a program with becker.jar as an external jar?

Question

I am setting up a program for a class I am taking. All the code has been provided and I have configured everything into Eclipse. I also had to use becker.jar as an external jar file in the Libraries -> Classpath. When I run the program an error occurs about a NullPointerException.

I already tried changing the becker.jar into the modulepath instead of classpath but then Eclipse cannot find the file. I also tried reinstalling becker.jar as well as redoing the entire setup for the project.

Here is the code I am trying to set up:

import becker.robots.*;

/* 
Starting Template:
This file was created in order to provide you with a pre made 
'starter' program
 */

public class Starting_Template extends Object {
    public static void main(String[] args) {
        City toronto = new City();
        Robot jo = new Robot(toronto, 3, 0, Direction.EAST, 0);
        new Thing(toronto, 3, 2);


        jo.move();
         jo.turnLeft();
    }   
}

When running this error shows up:

Exception in thread "main" java.lang.NullPointerException
at java.desktop/sun.font.FontDesignMetrics.getDefaultFrc(FontDesignMetrics.java:158)
at java.desktop/sun.font.FontDesignMetrics.getMetrics(FontDesignMetrics.java:279)
at java.desktop/sun.swing.SwingUtilities2.getFontMetrics(SwingUtilities2.java:1183)
at java.desktop/javax.swing.JComponent.getFontMetrics(JComponent.java:1646)
at java.desktop/javax.swing.plaf.basic.BasicLabelUI.getPreferredSize(BasicLabelUI.java:245)
at java.desktop/javax.swing.JComponent.getPreferredSize(JComponent.java:1680)
at java.desktop/javax.swing.JSlider.updateLabelUIs(JSlider.java:853)
at java.desktop/javax.swing.JSlider.setLabelTable(JSlider.java:824)
at becker.robots.x.<init>(SourceFile:32)
at becker.robots.RobotUIComponents.<init>(SourceFile:87)
at becker.robots.RobotUIComponents.<init>(SourceFile:110)
at becker.robots.City.a(SourceFile:228)
at becker.robots.City.<init>(SourceFile:97)
at becker.robots.City.<init>(SourceFile:47)
at Starting_Template.main(Starting_Template.java:10)

Answer 1

This is a bug. See for example https://issues.jboss.org/browse/PLANNER-255?_sscc=t - the becker.jar has nothing to do with it.