Inner Classes and Visibility

[jayesh bindra]

Hi,
Those who are studying for SCJP should analyze this piece of code carefully and try to predict the output.

class TestInner {
private int i=1;
class Inner {
int i=2;
void display() {
System.out.println(i+" "+TestInner.this.i);
}
}
TestInner.Inner doSomething() {
final int i=3;   // 1
return new TestInner.Inner() {
int i=4;
void display() {
int i=5;
System.out.println("anonymous"+i+TestInner.this.i+this.i+super.i); // 2
}
};
}
public static void main(String args[]) {
TestInner TI=new TestInner();
TestInner.Inner in=TI.new Inner();
in.display();
TI.doSomething().display();
}
}

Now for the question...
How does one print the value of i at 1 in the statement marked 2 ?
Regards,
Jayesh

[Hemal Mehta]

hmm.. interesting one!
Anyways the output is straightforward but ur second questtion is tricky!
2 1 & anonymous 5 1 5 2
I guess what happens here is that once you enturn into return
it hides the value if i even though it is final. Though you cannot chnage its value before that. I do no t belive ypu can print it's value unless you declare a diff varibale i1 and store it in that. Anyways would love to hear from other guys out there!

[jayesh bindra]

anyone else ???

[Stephen Minchin]

BTW, the output is 5142, not 5152.
I can't see any way for the variable i at //1 to be visible at //2,
The Final modifier lets the inner class access i, it being a local variable inside the method defining the inner class. But as soon as the inner class defines its version of i, the local i at //1 is totally inaccesable (unless you cheat and change it from i to j).
I'd love someone to prove me wrong.

[Bharatesh H Kakamari]

Isn't int i=5; in the display() method throwing error ?

[Aru Ven]

Hey Guys,
I'm getting an compilation error at
int i = 5 ;
error : Variable i is already defined in this method
if i comment this line evertthing is fine & the o/p is
2 1
anonymous0102
Aruna

[Vidya, Selvaraj]

Aruna,
I had the same problem when I used jdk1.2.1
jdk1.3 compiles fine
Vidya

[satishind Reddy]

hi Guys,
The output which i got is
2 1
anonymous5142
can any one tell me why others got 'anonymous5152' i think '4' is correct because inside anonymous class 'i' variable is having value '4'.
if i am wrong please explain to me....
regards
Satish