File APIs for Java Developers
Manipulate DOC, XLS, PPT, PDF and many others from your application.
The moose likes Java in General and the fly likes Null Pointer Exception Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login
JavaRanch » Java Forums » Java » Java in General
Bookmark "Null Pointer Exception " Watch "Null Pointer Exception " New topic

Null Pointer Exception

subodh varshney

Joined: Aug 01, 2005
Posts: 11
Dear All,
Please help me I m facing NullPointerException.

In following code i m retreiving some values from a table and storing them in a vector.
In case of response when it get null then loop goes to NullPointerException
so remaining variables(responseflag,url,urlflag,) does't get value so again it next code gives nullpointerexception.

for (int loop = 0; loop < result.size(); loop++) {
String keyword = null; String suffix = null; String username = null;
String password = null; String response =""; String responseflag = null;
String url =""; String urlflag = null;

try {
keyword = result.elementAt(loop).toString();
suffix = result.elementAt(loop + 1).toString();
username = result.elementAt(loop + 2).toString();
password = result.elementAt(loop + 3).toString();
response = result.elementAt(loop + 4).toString();
responseflag = result.elementAt(loop + 5).toString();
url = result.elementAt(loop + 6).toString();
urlflag = result.elementAt(loop + 7).toString();

catch (NullPointerException ex) {
Joanne Neal

Joined: Aug 05, 2005
Posts: 3742
You need to split each line so that you can check if has returned null before calling toString()


Sathya Srinivasan
Ranch Hand

Joined: Jan 29, 2002
Posts: 379
To expand on that, here's the Sherlock Holmes' rule to finding null pointers.

1. Print the stack trace (in your code you don't print anything. NEVER swallow a stack trace).
2. Look at the line where the exception happens.
3. Look at each segment in the code. A segment is essentially an object between dots. For example, in a code like a.someMethod().someOtherMethod(), there are 3 segments.
4. Take all but the last segment into consideration.
5. Eliminate segments that CANNOT be null (see if you have declared them already or if such methods will definitely return a value). Add log statements if needed.

Whatever remains, however confident you are, must be null and hence causing the NPE.

Cheers, Sathya Srinivasan - SCJP 1.2, SCWCD 1.2, SCMAD 1.0
Co-Author of Whizlabs SCMAD Certification Exam Simulator and SCMAD Exam Guide Book
I agree. Here's the link:
subject: Null Pointer Exception
It's not a secret anymore!