combination of += nad ++ operator

[H Gokulam]

class TestOperators {
public static void main ( String argv []) {
int i = 2, j = 2;
i += i++;
j += j--;
System.out.println( "i = " + i );
System.out.println( "j = " + j );
}
}

[H Gokulam]

The question is,
The output was i = 4 and j = 4.
Can somebody explain how is it arrived ?
Hari.

[Bogus user]

Wow that is a good one...
I was already to explain it, then I ran it...
int i = 2;
i += i++;
should be the same as:
i += i;
i++;
Right?
Actually it is the same as:
i = i + i++;
My guess would be:
i + i is evaluated and i++ is evaluated. Because of the order of operations the result of i + i is assigned to i and as a side effect the result of i++ is lost.
If some one could confirm my guess or corect me that would be great.
[ November 13, 2003: Message edited by: Jeff Swenson ]

[H Gokulam]

Jeff,
I was also expecting five.
i += i gives 4 and then i++ menas it should be 5.
Hari.

[H Gokulam]

Here is another one!
what will be the output if we change that line to
i = i++ + i++;
it is giving me 5.
Can somebody explain this!
Hari

[Tom Wolve]

Hi,
Let' try to make the code more readable to understand it.

 
....
i = 2;
calc = i++;   //-> calc is 2; i is 3;
calc = calc + i++; //-> calc is 5, i is 4;
i = calc; //-> i is 5

Hope this helps a bit
Tom

[Harwinder Bhatia]

I found this thread very helpful:
https://coderanch.com/t/190825/java-programmer-SCJP/certification/Array
Cheers
Harwinder