Null pointer Exception

[peiceonly]

Hi
Im beginner to java.
Just to in the stage of copy paste code .
Frequently seeing the exception Null pointer Exception.
What does this mean ?

[goldhouse]

This may be the first exception one find in his code , Best coding practices will make this exception disappear from your code.
This exception simply say ,that used object is null

String f = null ;
System.out.println("this will cause null pointer exception  "+ f.length());

to avoid that always use a null checking

String f = null ;
if(f!==null)
System.out.println("this will cause null pointer exception  "+ f.length());

[levent]

This may be the first exception one find in his code

Yes, this is one of the first things a Java programmer need to interpret. To understand it fully, you need to learn objects and their references.

When you see a null pointer exception. You should go to the line specified in the error and check if there might be any null references there. To do that you can add basic "if statements" for your object references used around that line (just like goldhouse did for f variable in the above code.). Once you found the null reference variable, you can fix the problem by changing the code there. This step is application specific: you might need to make sure that no null reference is there or you can allow null references but control the program flow for not getting a null pointer exception.

[g25451]

hello, how are you?

[mindblaster]

always avoid to Null Pointer Exception from this method

try{

// some code

}catch(NullPointerException e)
{
// code that shows error descroption
}

[Fubarable]

always avoid to Null Pointer Exception from this method

try{

// some code

}catch(NullPointerException e)
{
// code that shows error descroption
}

No, this is a very bad idea as this will just mask bad program design. Better is to write code that avoids NullPointerExceptions in the first place. With practice you will get better at doing this.

Edit: also, isn't this thread a bit long in the tooth to be replying to? It's over a year old.

[mindblaster]

i think when problem is solved or thread is old it should be locked.

because i never seen the date to thread when posting a reply ;)

[jason75]

hi, new , im having a problem with trying to get virtual radio on my lg
i down loaded to pc jad & jar files then to memory card then to phone it comes on for a sec then i get this message unaccepted exception the application caused an error and will be terminated nullpointer exception
please help its driving me crazy want to listen to radio on phone
thanks

[Fubarable]

Is this a program that you yourself have written in Java? If so, the error message will tell you which line in the source code is causing the exception. If not, then not much we can do other than to tell you to contact your vendor. This would be way beyond the scope of this forum.

Edit: well, you never responded, so I assume that it's the latter issue, that you're not a Java developer but rather a consumer in which case you should contact the vendor. If I'm wrong and you are a developer, then please start a new thread for your question. Given the age of this one, I'm locking it.