NullPointerException

[subhasish nag]

when I am working on the code given below NullPointerException is throwing ..
code1#
class Ntry

{


public static void main(String args[])

{
String A=null;
String B=null;
String result= A.concat(B);
System.out.println(result);

}
}
But when I am trying with this output nullnull is coming

class Ntry

{


public static void main(String args[])

{
String A=null;
String B=null;
String result= A+B;
System.out.println(result);

}
}
Kindly explain

[Maneesh Godbole]

when I am working on the code given below NullPointerException is throwing ..

That is because you are trying to invoke a method of an object which is null

String result= A.concat(B);

But when I am trying with this output nullnull is coming

You have the following code:

String A=null;
String B=null;
String result= A+B;
System.out.println(result);

The println method checks if the String is null. If it is, it allocates the value "null" (String value) to the null String. That is why you get nullnull.

[Dariusz Kordonski]

Maneesh has explained your problem very well, just if you're courious why is it happenning - check out the Java Language Specification v3 $15.18.1.1
[ August 08, 2008: Message edited by: Dariusz Kordonski ]