post Increment problem

Question

Possible Duplicate:
Why does this go into an infinite loop?

public class loop
{

    public static void main(String[] args)
    {
        int k=0;
        for (int i = 0; i < 6; i++) 
        {
            k = k++;
            System.out.println(k);            
        }
    }
}

out put :

Can You Please explain me why above resulting zeros even am incrementing k value and assigning it to k.

score 8 · Answer 1 · answered Jul 19 '11 at 12:48

This line is a no-op:

k = k++;

It's equivalent to:

int tmp = k;
k = k + 1;
k = tmp;

You're incrementing k, but then assigning the original value back to k.

I hope you don't really have code like that... while the behaviour of this code is well-defined in Java, it's (clearly) confusing.

score 0 · Answer 2 · answered Jul 19 '11 at 12:49

0

may be your are trying to get something like

int k=0;
    for (int i = 0; i < 6; i++) 
    {
        k = ++k;
        System.out.println(k);            

    }

answered Jul 19 '11 at 12:49

Rasel

15,499
6
40
50

I think `++k;` is better than `k = ++k;` – Armen Tsirunyan Jul 19 '11 at 12:50
thanks for your reply. But i wanted know why k is not incrementing. – vedamurthy Jul 19 '11 at 12:53

score 0 · Answer 3 · answered Jul 19 '11 at 12:55

0

You can even better use:

for(int i = 0; i < 6; i++)
{
    System.out.println(i);
}

answered Jul 19 '11 at 12:55

Eng.Fouad

115,165
71
313
417

i wanted to know reason behind that. public class loop { public static void main(String[] rgs) { int k=0,j=0; for (int i = 0; i < 6; i++) { j= k++; System.out.println(k+" "+j); } } } – vedamurthy Jul 19 '11 at 12:57

score 0 · Answer 4 · answered Jul 19 '11 at 12:57

The k++ piece of code increments the value of k by 1 and then returns the pre-incremented value. Thus, the following line:

k = k++;

adds one to k, and then assigns the original value of k (returned by k++) to k. This means k winds up with it's original value.

public class loop {
    public static void main(String[] args) {
        int k=0;
        for (int i = 0; i < 6; i++) {
            k++; // increments k by 1
            System.out.println(k);            
        }
    }
}

score 0 · Answer 5 · answered Jul 19 '11 at 12:58

public class loop
{

    public static void main(String[] args)
    {
        int k=0;
        for (int i = 0; i < 6; i++) 
        {
            k++; // k increased. No reasons to assign anything
            System.out.println(k);            
        }
    }
 }

k++ increase k, then return old k , then you asign this old k to k and k is 0 again

post Increment problem

5 Answers5