get value from table

I want to get value from table.I tried like that

mystring=dsk1.klm.Table_Grid.getModel().getValueAt(row,column).toString();

and it gived this error:Exception in thread "Thread-3" java.lang.NullPointerException

is there a way to get value from table?

please help me!

[298 byte] By [frknmla] at [2007-11-27 11:26:51]