CODEWITHSUNDEEP
javafor-looppost-incrementpre-increment
shryesh.k
shryesh.k

Reputation: 51

A program with for loop

I was writing a for loop program when this code came across my mind.

for(int i=1; i<=10; i++,i++)

The program works fine and the output is also correct. But then I tried the following code:

for(int i=1; i<=10; ++i,++i)

for(int i=1; i<=10; ++i,i++)

for(int i=1; i<=10; i++,++i)

To my amazement, all of them produce the same output, 1 3 5 7 9. Now my question is, how exactly do for loops work and why did all the code produce the same output when I used pre-increment and post-increment in the same for loop?

Upvotes: 0

Views: 93

Answers (3)

pauljwilliams
pauljwilliams

Reputation: 19225

Using multiple elements seperated by a comma is only (potentially) problematic if the order of their execution matters.

If you're not using the result of a post/preincrement, and the only thing that matters is the increment itself, then clearly the net result will be the same - adding 2.

Upvotes: 0

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35577

i++ means use then increment with a copy and incremented happen later in that line

++i means increment and use without a copy and increment happen immediately.

That's is the deference here.

Upvotes: 0

EpicPandaForce
EpicPandaForce

Reputation: 81578

it's equivalent to

int i = 1;
while(i <= 10)
{
   //stuff would happen here but these loops are all empty
   i++;
   i++;
}

and

int i = 1;
while(i <= 10)
{
   //stuff would happen here but these loops are all empty
   ++i;
   ++i;
}

and

int i = 1;
while(i <= 10)
{
   //stuff would happen here but these loops are all empty
   ++i;
   i++;
}

and

int i = 1;
while(i <= 10)
{
   //stuff would happen here but these loops are all empty
   i++;
   ++i;
}

In which case whether it's pre-increment or post-increment, it doesn't matter at all. It just increments the value of i by 1.

Upvotes: 5

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