Question

Hey everyone, I am trying to run the following program, but am getting a NullPointerException. I am new to the Java swing library so I could be doing something very dumb. Either way here are my two classes I am just playing around for now and all i want to do is draw a damn circle (ill want to draw a gallow, with a hangman on it in the end).

package hangman2;  import java.awt.*; import javax.swing.*;  public class Hangman2 extends JFrame{     private GridLayout alphabetLayout = new GridLayout(2,2,5,5);     private Gallow gallow = new Gallow();      public Hangman2() {          setLayout(alphabetLayout);          setSize(1000,500);         setVisible( true );      }      public static void main( String args[] ) {         Hangman2 application = new Hangman2();      application.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );     } }   package hangman2;  import java.awt.*; import javax.swing.*;  public class Gallow extends JPanel {     private Graphics g;      public Gallow(){         g.fillOval(10, 20, 40, 25);            } } 

The NullPointerException comes in at the g.fillOval line.

Thanks in advance,

Tomek

Answer 1

You’re getting NPE because g is not set, therefore, it’s null. Furthermore, you shouldn’t be doing the drawing in the constructor. Overload paintComponent(Graphics g) instead.

public class Gallow extends JPanel {     public paintComponent(Graphics g){         g.fillOval(10, 20, 40, 25);            } } 

I’d also look into BufferedImage.