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java.lang.NullPointerException?

Posted on 2002-04-09
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Last Modified: 2010-03-31
Please explain this error for me?
My code:
...
try {
     if(mySocket!=null){
          remoteIn = mySocket.getInputStream();
     }
} catch (Exception e) {
     System.out.println("Here's error: "+e.toString());
}

Print out: Here's error: java.lang.NullPointerException

What makes that error?
Thanks in advance.
GN

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Question by:tgiangn
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Expert Comment

by:CEHJ
ID: 6928280
As has been said already, call e.printStackTrace()instead and post the error output.
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Expert Comment

by:saxaboo
ID: 6928286
In a single-threaded environment, your test makes sure that mySocket is not null before invoking getInputStream, so the error means that getInpuStream itself throws an exception ...

In a multithreaded environment, your test doesn't seem safe (at least you did not provide enough code). Indeed, if mySocket is used by mutiple threads, it could be nulled out by another thread between your if() statement and your call to getInputStream.

=> 2 questions
1. are you multithreaded or not ?
2. could you post more code, such as socket opening ?

-S
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by:Moondancer
ID: 6956668
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by:Venci75
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No comment has been added lately, so it's time to clean up this TA.
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Finalized as proposed

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