Question

here’s the code which I don’t quite understand:

for(int i = 0; i < (i = 1); i++)
            System.out.println("FOR " + i);

I expected this code not to show anything, but instead it outputs ‘FOR’ one time.

I was thinking that i < (i=1) should compare the value of i with the result of the assignment i=1 which is 1 -> so 1<1 which is false -> exit the loop without showing anything.

Maybe the way this comparison is made is different than I understand it. Thank you!

Answer 1

i < (i = 1)

This will be evaluated as: –

0 < (i = 1)  -->   0 < 1  --> true, so for loop executes

On next run, when i++ is executed and i becomes 2 (Since, i was 1 from the (i = 1) assignment on the previous run of loop.)

So, i < (i = 1)

evaluates to: –

2 < 1 --> false.

So, for loop exits.

Note: – In your condition part (i < (i = 1)), before the assignment (i = 1) happens, the LHS has already been evaluated to be 0, and stored in memory. So, it will remain 0. Its all about the order of evaluation. So the assignment i = 1 will not affect the value of expression on LHS.