need help in identifying what's wrong with my codes.is giving the following exception after running the code:
the exception is:
Exception in
thread "main" java.lang.NullPointerException
at java.awt.Container.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at javax.swing.JDialog.addImpl(Unknown Source)
at java.awt.Container.add(Unknown Source)
at TestDialog.<init>(TryDialog.java:28)
at TryDialog.<init>(TryDialog.java:68)
at TryDialog.main(TryDialog.java:91)
the code is: