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NullPointer Exception in JSP

milan doshi
Ranch Hand

Joined: Nov 03, 2000
Posts: 43
I am trying to develop a simple shopping cart using JSP(using Tomcat 3.1).
I have generated CheckBoxes , which when checked , the corresponding items are selected.
I am retrieving those values through the following commands.
String basket[]=request.getParameterValues("c1");
out.println("<hr>Items selected "+basket.length);
This works fine only when 1 or more items are selected. If however , NO items are selected (i.e no checkboxes are checked) than I get a NullPointer exception.
The reason for this is basket.length!!!
But why ? Why cant I simply get an output as follows?
Items selected null
Thanx in Advance

maha anna
Ranch Hand

Joined: Jan 31, 2000
Posts: 1467
This is a very common and famous experience which I think all java people encounter. The best practice of java coding is, before you invoke any method on a reference, check if the reference is NOT NULL and then do the other checks. This is where the '&& CONDITIONAL CHECK' comes for help. Just change your code slightly like this. Now you won't get NullPointerException.
maha anna
milan doshi
Ranch Hand

Joined: Nov 03, 2000
Posts: 43
Thanx for the help,
I agree. Here's the link:
subject: NullPointer Exception in JSP
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