tgiangn
asked on
java.lang.NullPointerException?
Please explain this error for me?
My code:
...
try {
if(mySocket!=null){
remoteIn = mySocket.getInputStream();
}
} catch (Exception e) {
System.out.println("Here's
}
Print out: Here's error: java.lang.NullPointerExcep
What makes that error?
Thanks in advance.
GN
My code:
...
try {
if(mySocket!=null){
remoteIn = mySocket.getInputStream();
}
} catch (Exception e) {
System.out.println("Here's
}
Print out: Here's error: java.lang.NullPointerExcep
What makes that error?
Thanks in advance.
GN
CEHJ
As has been said already, call e.printStackTrace()instead
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
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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