Question

I’m getting the following NullPointerException:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.foo.JawsFileChooser.a(SourceFile:28)
    at com.foo.JawsFileChooser$1.actionPerformed(SourceFile:91)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2018)
    [...snip...]

when users click a button in my app and follow a certain set of steps. But Line 28 in JawsFileChooser.java is the line which defines the class:

public class JawsFileChooser extends JPanel implements SwingConstants, DebugConstants {

. What could I take a look at to figure out why this is happening?

thanks in advance for any help.

Answer 1

What could I take a look at to figure out why this is happening?

You could take a look at SourceFile:28, it is part of com.foo.JawsFileChooser.a and dereferencing a reference that is null

EDIT:
I have seen the first line of class reported in stacktrace in presence of anonymous inner classes. For example the following code

 1 import java.util.concurrent.*;
 2 
 3 class An {
 4 
 5  private String foo()
 6  {
 7      return "foo";
 8  }
 9  
10  public static void main(String[] args) {
11      final An an = null;
12      (new Callable<String>() {
13          public String call() {
14              return an.foo();
15          }
16      }).call();
17  }
18 }

Results in

javac -g An.java && java -cp . An
Exception in thread "main" java.lang.NullPointerException
    at An.access$000(An.java:3)
    at An$1.call(An.java:14)
    at An.main(An.java:12)

The synthesized method name is printed but the line number is similar to your case. I would look at com.foo.JawsFileChooser$1.actionPerformed(SourceFile:91)