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NullPointerException ??

 
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How come a nullpointer exception has occurred i this program !!!

 
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are you sure this program compiles??
 
Ankitt Dhebarr
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I am sorry i had misprinted somthing !!! Now I am getting A NUllPointerException !!! Why is it ?? Can you help me out please !!

 
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Your Integer a, is a Wrapper but has not been initialized, therefore by default it will be null;
 
Ankitt Dhebarr
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The wrapper variable is not 'i' its 'a' . I am sorry !!! Now can anyone help me out !!

 
Stephen Davies
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Even so Integer a is a wrapper, and if you do not initialize it it will be null. Thus, when you attempt:



you are saying b = null + y
 
Ankit Garg
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Well to be more specific, when you say

b = a + y

The compiler would insert unboxing code so the code means this

b = a.intValue() + y

since a is null, so the statement would look as

b = null.intValue() + y

and we know that calling a method on a null reference results in a NullPointerException...
 
Ankitt Dhebarr
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Thanks a lot to everyone for helping me a lot !!

 
Ankit Garg
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Ankitt why do you use quote tags to type your message??
 
Ankitt Dhebarr
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So What should I use ?? Actually I am new so I dont know much about it !!
 
Ankit Garg
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Just simply write your message. The quote tag is used if you want to quote what someone else had written...
 
Ankitt Dhebarr
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OK !! Thanks I will take care from next time !!
 
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