Sample source code for GUI

hi

I am fairly new to designing GUI in JAVA . My applicaiton involves a big form with alot of choice list[ around 7 choice list ] which r populated using queries from database and also when an item is selected from the choice list , a query is ran which would refresh the screen with the result of the query ., this query would be based on the items selected in the choice lists.

I tried implementing it, i was able to populate my choice list with the things i need from the DB using the query . but when i just select anything from the choice list, it would throw me a :

java.lang.NullPointerException

I am suprised cause, when i select from one choice list, i wouldnt get this error. Also i have not written any event .

please help .. really important .... or just suggest me some source code which i can study and learn !!! please ....

Thanks in advance

[907 byte] By [vikrammodi] at [2007-9-26 4:20:21]