x = (x = 1) + (x = 2) * (++x) * (x++) - Why is the output of this expression 19?

Question

I executed the code and output was 19, but I don't understand why.

public static void main(String[] args) 
{
    int x = 0;
    x = (x = 1) + (x = 2) * (++x) * (x++);
    System.out.println(x);
}

running the program won't really answer his questions though ;) Only you can do that. — Mark, Jul 03 '17 at 10:32
That's not an answer to my question. You already told us what the result actually is. I don't need to run the program to know that. I asked what you think it should be, and you haven't answered that. I also asked you why, and you haven't answered that either. — user207421, Jul 03 '17 at 10:33
possible duplicate https://stackoverflow.com/questions/2371118/how-do-the-post-increment-i-and-pre-increment-i-operators-work-in-java — Pshemo, Jul 03 '17 at 10:39

score 8 · Answer 1 · answered Jul 03 '17 at 10:27

8

You evaluate the operands from left to right, and then evaluate the multiplication operators before the addition operator:

x = (x = 1) + (x = 2) * (++x)  *      (x++);

       1    +    (2    *   3   *       3     )  = 19

    assignment          pre            post
    operator            increment      increment
    returns the         returns the    returns the
    assigned value      incremented    value before
                        value          it was incremented

answered Jul 03 '17 at 10:27

Eran

387,369
54
702
768

then it should increment another time for x++ – mahdi Jul 03 '17 at 10:34
1

@mahdi x++ increments x to 4, but returns 3. – Eran Jul 03 '17 at 10:35
@mahdi https://stackoverflow.com/a/2371162 – Pshemo Jul 03 '17 at 10:38
The last `++` happens before the assignment of 19 to `x`, so the 4 is overwritten. – Ole V.V. Jul 03 '17 at 10:48

score 2 · Answer 2 · answered Jul 03 '17 at 10:28

2

its evaluated like this -

1+2*3*3

(x=1) - first x is set t 1
(x=2) - then x is set to 2
(++x) - then x is incremented to 3; pre-increment and affects the equation in this case (x++) - the last was post increment; no effect on the equations

answered Jul 03 '17 at 10:28

Razib

10,965
11
53
80

score 2 · Answer 3 · answered Jul 03 '17 at 10:32

2

as per my knowledge:

1 + 2*3*3 = 19

answered Jul 03 '17 at 10:32

shivam pandey

21
1

x = (x = 1) + (x = 2) * (++x) * (x++) - Why is the output of this expression 19?

3 Answers3