Why the result is 1,0

[weyman tan]

Why the result is 1, 0 in following code

static class C {
		static int f1(int i) {
			System.out.print(i + ",");
			return 0;
		}

		public static void main(String[] args) {
			int i = 0;
			int j = 0;
			j = i++;
			j = j + f1(j)
			i = i++ + f1(i);
			System.out.println(i);
		}
	}

is any one tell me why, thank you very much

[John Jai]

Hello Weyman, welcome to the Ranch

An outer class cannot be declared static, so the code won't compile itself. I have removed it.

public class C {

	static int f1(int i) {
		System.out.print(i + ",");
		return 0;
	}

	public static void main(String[] args) {
		int i = 0;
		int j = 0;
		// i is incremented from 0 to 1 in the below statement. But since pre-fix, 0 is the value assigned to j
		j = i++;
		// The call of f1(j) prints 0 in the f1() method
		j = j + f1(j) ;

		// The call of f1(i) prints 2 in the f1() method. But the f1(int i) method returns 0 to the caller.
		// Hence the expression i = 1 (increment i) + f1(2) becomes i = 1 + 0;
		i = i++ + f1(i);
		System.out.println(i);
	}
}

The questions tests the post fix and prefix increment operators. I have commented alongside the program the values and why it's printed so. The output I get is 0,2,1.

Next time while posting please UseCodeTags...

[weyman tan]

After see your answer, I know why and the original code is

class C{
static int f1(int i) {
System.out.print(i + ",");
return 0;
}
public static void main (String[] args) {
int i = 0;
i = i++ + f1(i);
System.out.print(i);
}}

so the result is 0,1

in order to study why, I add some code in it which result is 0,2,1.
However thank you very much

[Mohamed Sanaulla]

Hi Weyman, I have added the code tags for you. Please post your code within the code tag. This makes the code more presentable.

[John Stark]

so the result is 0,1

Should it give 1,0

John

[O. Ziggy]

John Jai wrote:Hello Weyman, welcome to the Ranch

		// The call of f1(i) prints 2 in the f1() method. But the f1(int i) method returns 0 to the caller.
		// Hence the expression i = 1 (increment i) + f1(2) becomes i = 1 + 0;
		i = i++ + f1(i);
		System.out.println(i);
}

I dont understand where the 1 is coming from. When it gets to this point

i = i++ + f1(i);

i is 1. So if f1 returns 0, should shouldn't i be 2 because of the i++? i.e. the output to be 0,2,2? See comments below

 j = i++;   //After this statement j=0 i=1
            j = j + f1(j);  //After this statement j=0 i=1
            i = i++ + f1(i);  //i++ means i is now 2. The call f1(2) prints 2 and but returns 0 so i=2 and j=0
            System.out.println(i);  //prints 2?

[fred rosenberger]

I dont understand where the 1 is coming from. When it gets to this point

i = i++ + f1(i);

i is 1. So if f1 returns 0, should shouldn't i be 2 because of the i++? i.e. the output to be 0,2,2? See comments below


This more or less simplifies to

i = i++;

and we have a FAQ on why that leave i how it was...but basically, assuming i is one before we get to this line

1) we have a post-fix operator, so get the value of i. It is 1. Remember that value for a moment.
2) We now increment i, making it 2.
3) We now assign THE VALUE WE REMEMBERED to i. the value was 1, so assign 1 to i
4) i is now 1.

So for a brief, brief instant, after the increment operator but before the assignment, i IS equal to 2, but we then reset it back to 1.