How to avoid Java.lang .nullpointer.exception

[Berend Rah]

I have some trouble with an applet running a method which works well when
tested on
its own as a standalone application. However, when I try to pass values by
scrollbar and submit button to it, the method is not carried out.

Instead I get java.lang.nullpointer.exceptions at various points.

I am not familiar with threads and how to make them save. Any feedback or
suggestions would be appreciated.

Berend