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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?

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  • 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? Commented Apr 20, 2015 at 11:58
  • 1
    when x==9 the condition is still valid so x is incremented again, that is why it prints out 10 Commented Apr 20, 2015 at 11:58

2 Answers 2

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3

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

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3 Comments

Additional note: Remember that the Do statement is executed before the while condition is evaluated.
@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.
I know (since it's <=) but I wanted to state this anyway. Therfor it's a note on your answer ;).
1

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

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