Null pointer exception

[Brad Whiting]

Hello all,   I am a rookie java servlet programmer, and I am getting an error that is confusing me.   I have created an HTML form that has a large number of check boxes.  The idea being that each checkbox represents a column in a database.  I hope to structure an sql call that will include only the checked columns.  The odd thing about the program is that it works fine if I check every box.  If I leave any unchecked I get a null pointer exception at the point in the code where I am checking to see if the box is checked.   This is an example of my html input statement:   <input type=checkbox name=cpumod value="yes"> CPU Model   This is an example of my servlet code that checks:   String b       = req.getParameter("cpumod");      if (b.equals("yes") == true)                         sqlcom2 += ",\n CPUMOD";       This is the exception I see in my logs:   Instantiate: DBgetsysid                                                                       Sep 24, 2001 17:57:08.357 PM  12d7140000000019:Thread-13:130899e0 StrictServlet X doService                                     java.lang.NullPointerException                                .at DBgetsysid.doPost(DBgetsysid.java:68)                                                   BTW I am using doPost to process the form.  Can anyone help me with my mistake?  I just can't see it.     TIA, brad