why is the for loop happening 3 times when the if statement is only true twice?

Question

why is my code executing the body inside the for loop 3 times?

should it not only happen 2 times?

why 3 times?

when I run this I get:

"4 divided by 2 the remainder is

0

4 divided by 3 the remainder is

1

4 divided by 4 the remainder is

0

loop has exited out of for loop because D is now 5 count is now 2.

code inside if statement should've happend 2 times

value of N is 4"

public class forIf {

public static void main (String[] args) {

int D;
int N = 4;
int count;

count = 0;

for (D = 2; D <= N; D++) {
  if (N % D == 0)
    count++;
    System.out.println( N + " divided by " + D + " the remainder is");
    System.out.println( N % D );
}
System.out.println("loop has exited out of for loop because D is now " + D);
System.out.println("count is now " + count + ". code inside if statement should've happend " + count + " times");
System.out.println("value of N is "+ N);
}
}
// shouldn't the code inside the if statement only happen twice?
// because N % D is only true twice?
// why is it running that block 3 times?

Because Java is not Python, it pays no attention to indentation. Your `if` covers only `count++`, not the two prints, which are outside the `if`. Add curly braces to fix this problem. Voting to close as a typo. — Sergey Kalinichenko, Sep 07 '18 at 14:59
To strengthen what dasblinkenlight says: *always* use optional curly braces (on for, if, while etc), to *avoid* the problem in the first place. — Andy Turner, Sep 07 '18 at 15:05
Ah ok. So always use curly brackets to enclose even 1 line of code. But if there aren't any curly brackets, it would only run that one line? Ah ok I just saw the other duplicate question. Thanks again! — javastudent, Sep 07 '18 at 15:13

xtratic · Answer 1 · 2018-09-10T19:24:00.023

why is my code executing the body inside the for loop 3 times?

Here is what the loop variables are each time you loop

int N = 4;
for (D = 2; D <= N; D++) ...

Loop 1: D = 2 , 2 <= 4 is true  
Loop 2: D = 3 , 3 <= 4 is true  
Loop 3: D = 4 , 4 <= 4 is true

This is why your loop happens three times.

As for this why the

code inside if statement should've happend 2 times

As others have also pointed out, the only code inside your if-block is count++; if you want to include the printlns then they must be inside braces of the if-block.

if (N % D == 0) { // <-- brace
    count++;
    System.out.println( N + " divided by " + D + " the remainder is");
    System.out.println( N % D );
} // <-- brace

score 0 · Answer 2 · answered Sep 07 '18 at 15:00

0

Your if has only one statement count++. The two print statements are not part of it. You need to enclose the block within {..}

for (D = 2; D <= N; D++) {
  if (N % D == 0) {
    count++;
    System.out.println( N + " divided by " + D + " the remainder is");
    System.out.println( N % D );
  }
}

answered Sep 07 '18 at 15:00

Thiyagu

17,362
5
42
79

wow for some reason i did that earlier and it still didn't work as I intended. But the extra 2 curly brackets fixed it. Thank you! – javastudent Sep 07 '18 at 15:06

score 0 · Answer 3 · answered Sep 07 '18 at 15:00

When the contents of your if (and while and for and so on) are more than one line, you need to enclose them in brackets ({}). Actually, you should always do this, even when it's just one line, because doing so is easier to read and less bug-prone. Your if should look like this:

for (D = 2; D <= N; D++) {
  if (N % D == 0) {
    count++;
    System.out.println( N + " divided by " + D + " the remainder is");
    System.out.println( N % D );
  }
}

why is the for loop happening 3 times when the if statement is only true twice?

3 Answers3