Java plus Operator

Question

class ExcerciseLib1 {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        int x = 1;
        while (x < 10) {
            x = x + 1;
            if (x > 3) {
                System.out.println("big x");
            }
            if (x < 4) {
                System.out.println("big 1");
            }

        }

    }

}

In the code above, big 1 get's output 2 times, and big x gets output 7 times. I don't quite understand why big x outputs 7 times, shouldn't it be 6 times?

I get that

if (x < 4) {
                System.out.println("big 1");
            }

outputs "big 1" twice because using the loop,

x = 1 + 1 equals 2 which is less than 4,
x = 2 + 1 equals 3 which is less than 4.

So for

if (x > 3) {
            System.out.println("big x");
        }

Shouldn't the loop only output it 6 times?

x = 3 + 1 equals 4, 4 is greater then 3, so output big x.
x = 4 + 1 equals 5, 5 is greater than 3, so output big x.
x = 5 + 1 equals 6, 6 is greater than 3, so output big x.
x = 6 + 1 equals 7, 7 is greater than 3, so output big x.
x = 7 + 1 equals 8, 8 is greater than 3, so output big x.
x = 8 + 1 equals 9, 9 is greater than 3, so output big x.
x = 9 + 1 equals 10; but the loop states x < 10

I'm getting brain stumped on this one. Am I understanding the "x = x + 1" expression wrong?

change into System.out.println(x+",big x"); you'll get answer. — Kent
– Kent, Commented May 22, 2014 at 23:13

Dawood ibn Kareem · Accepted Answer · 2014-05-22 23:10:45Z

4

The loop condition is only run at the start of each iteration. The loop doesn't magically end partway through if the condition becomes false in the middle of an iteration.

So in the final iteration, x is intially 9, and then you add 1 to make it 10, and the loop continues on.

answered May 22, 2014 at 23:10

Dawood ibn Kareem

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1 Comment

some random dude Over a year ago

Ohh ok I understand it now. Thanks for the clarity guys!

Matt Coubrough · Accepted Answer · 2014-05-22 23:12:33Z

1

The x < 10 is evaluated before the increment...

so when x == 9, it enters the body of the loop, increments x to 10 then prints the output, then evaluates the conditional again

answered May 22, 2014 at 23:12

Matt Coubrough

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