Post Increments

Question

I'm trying to understand post incrementation at the hand of these 3 examples. But I have difficulties trying to understand the last one.

1.

int x = 0;
x++;
System.out.println(x); //prints out 1

2.

int x = 0;
x = x++;
System.out.println(x); //prints out 0.

x in itself contains 1, but not the left side reference variable pointing to x seeing it's post-incrementation. So the original value is returned.

3.

int x = 0;
do {
    x++;
} while (x <= 9);
System.out.println(x); // prints out 10

But according to my reasoning based on the first 2 examples it should print out 9. x in itself first contains 1, then 2, 3, 4, 5, 6, 7, 8, 9. Could someone please explain the output for the last example?

Example 3 has nothing to do with example 2, since there is no `x=x++;` code inside. It refers only to example 1, so the result is correct, isn't it? — Thomas Weller, Apr 20 '15 at 11:58
when x==9 the condition is still valid so x is incremented again, that is why it prints out 10 — Alexandru Cimpanu, Apr 20 '15 at 11:58

score 3 · Accepted Answer · answered Apr 20 '15 at 11:57

3

As long as x <= 9, the while loop won't be terminated, so x must by 10 after the loop.

answered Apr 20 '15 at 11:57

Eran

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Additional note: Remember that the Do statement is executed before the while condition is evaluated. – GregD Apr 20 '15 at 12:00
1

@GregD In this case it makes no difference. Even if the loop was `while (x <= 9) {x++;}`, you'd still get 10 after the loop. – Eran Apr 20 '15 at 12:02
I know (since it's <=) but I wanted to state this anyway. Therfor it's a note on your answer ;). – GregD Apr 20 '15 at 12:05

score 1 · Answer 2 · answered Apr 20 '15 at 12:01

1

The loop continues until x > 9. The first value for this condition to be true is 10.

answered Apr 20 '15 at 12:01

Thorsten Dittmar

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Post Increments

2 Answers2