How increment operator(++) works

[Ram Chhabra]

Hi,

I am confused in below code because according to me output should come as 2 but it is coming as 1, can you please explain why. Code is below:

          int i = 1;
        i = i++; 
        System.out.println("i = "+i);  
  

Thanks,
Ram

[David O'Meara]

"Ram Realism",
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[Ankit Garg]

It goes like this

first i is set to 1

int i = 1;

then i = i++ is executed. since it uses post-fix ++, so 1 is used in the expression.

so it looks like this

i = 1

but the assignment will not be done this time, first i will be incremented by 1(post-fix ++), so i becomes 2. Then the assignment above will work and 1 will be assigned to i. So finally i is 1..

[Christophe Verré]

It's also explained here.

[Anton Coverdale]

Note if you take the i= part off the second line, to end up with this:

int i = 1;
        
i++;
     
System.out.println("i = " + i); 

You end up with i = 2 like you were expecting.

[Mohammad Khan]

int x;
int i = 0;    // initial assignment
 
i++;          // post increment, at the end of executing i is 1
x = i++;      // assign x to i and then increment i
              // at the end of executing this statement x is 1 and i is 2
 
i = 0;        // re-assign i to 0
++i;          // pre increment, at the end of executing i is 1 
x = ++i       // first increment i and then assign x to i
              // at the end of executing this statement x is 2 and i is 2

I hope this would help to understand post-increment and pre-increment

Thanks,
Mohammad