Question

I am a complete beginner and I’m trying to follow the logic behind this code snippet.

int x = 12;
do {
    for (int w=9; w<x; w++)
        System.out.print(w+” ”);
    --x;
    System.out.println(x);
}while (x>7);

When I run it, the answer is as follows:

9 10 11 11
9 10 10
9 9
8
7

If someone could explain how to read the code step by step in a simple way I would be very happy!

Answer 1

int x = 12; declare new local variable, called x

do { begins new do...while loop

for (int w=9; w<x; w++) begins new for loop which will iterate until value of variable w is less then value of variable x. After each iteration of this loop variable w will increase its value (by w++). Initial value of variable w is 9 (int w=9).

System.out.print(w+” ”); this one prints out to console current value of variable w plus one white-space after that

--x; this one decreases value of x variable. It is such called prefix version of operation --

System.out.println(x); prints value of x variable to console and returns carriage

} end of for loop code block (fixed thanks to Chris)

} while (x>7); end of while code block with condition on which loop will end: until value of variable x is more then 7 loop will run.

UPD: More specifically explaining output result:

1) 1-st iteration of do loop. We have x == 12:

iterations of internal for loop:

1.1) w == 9 , 9 < 12 => outputs 9 to console

1.2) w++ => w == 10, 10 < 12 => outputs 10 to console,

1.3) w++ => w == 11, 11 < 12 => outputs 11 to console,

1.4) w++ => w == 12, 12 == 12 => ends for loop

2) for loop ends. --x => x == 11 , outputs 11 to console and returns carriage, so we have line 9 10 11 11

3) begins new iteration of do ... while loop with x == 11 and so on until x became equals to 7.