Post increment in for loop in java

Question

int num=0

for(int i=0;i<5;i++)
{
    num = num++;
    system.out.println(num);
}

I am little confused with the output of above program. It prints five times 0 in output. Why isn't the num variable incremented in the loop?

@Renzo,@Amit .. I forgot to add print statement.Now it is there. — vishal shikotara, Aug 19 '16 at 19:47

score 1 · Answer 1 · answered Aug 19 '16 at 19:12

1

num++ will return the current value of num (i.e., 0), and then increment num. However, since you re-assign this to num, you overwrite the incrementation with the previous value, so num remains 0 throughout the program.

answered Aug 19 '16 at 19:12

Mureinik

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@MouseEvent I thought I did. What would you like elaborated? – Mureinik Aug 19 '16 at 19:24
I'd say, show step-by-step what happens to `num`. But maybe the linked duplicate may be enough. – Mordechai Aug 19 '16 at 19:30

score 0 · Answer 2 · edited May 23 '17 at 11:51

0

You need to increment with ++num. For example:

int num=0;

for(int i=0;i<5;i++)
{
    num = ++num;
}

System.out.println(num);

Output:

Though you don't need to reassign it every time, num++ alone would be the proper way to do it.

See previous answer: Difference between ++var and var++

edited May 23 '17 at 11:51

Community

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answered Aug 19 '16 at 19:32

Nick M.

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score 0 · Answer 3 · answered Aug 19 '16 at 20:33

You should know the difference between num++ and ++num. In your case, at first num is set to 0. When you say num = num++;, it first assgin 0 to num (left one), and then apply ++. It really does not matter what the right part of equation does... So that's the reason you've got 5 0's.

Post increment in for loop in java

3 Answers3