public class Test {
public static void main(String[] args) {
int a;
// for( a=0; a<5; a++ ){}
try {
a=10;
} catch (Exception e) {
//TODO: handle exception
}
System.out.println(a);
}
}
In the above code, initialization to var a by for loop persists while printing it, but not with try block.
The java compiler doesn't know what is going to happen in the try block.
The whole point of the try/catch is: there is some code that might execute fine, or might not. Therefore the assignment to a inside the try block is not guaranteed to happen, therefore the following read access to a might find it as (still) not initialized.
The real answer: there are many situations where a human reader can see "there is no problem here". But the java compiler fails to recognize that special case. Of course, one could write a compiler that detects "a is assigned a value, and that code will never throw an exception". But the java compiler isn't written that way. That is all there is to this.
intcannot have aNullPointerExceptionas it cannot be null. As far as the compile is concerned, there is a code-path (the catch block) that doesn't initializea, so it simply disallows it.