It is Very simple but intresting...........plz give me ans of my simple pro

Question

<h4>
Hi friends ,
I have some probs. that i can not understood the
logic behind this......if any one know plz reply me.
This is one sample prog.
class test
     public static void main(String str[])
          int i=10;
          int j=i++;
          System.out.println(j + " " + i);
output : i=11 and j=10
=================================================================
now if i change this prog.
class test
     public static void main(String str[])
          int i=10;
          i=i++;
          System.out.println(i);
now it display value of i is : 10
why ? the rule of post increment is that first
assign the value and then increment the value of the
variable. But when i m using same var. as left side
it will not increment.
Can any one help me why is it?
plz reply me if u know...
Thank You in Advance.
</h4>

Answer 1

ThomHehl wrote:
I'm just kinda spitballing here, but you have to think about the way this gets translated into machine code.
When you do an assignment, it moves a value from one memory location to another. When it sees both assignments and that there are further operations to do on the sending part, in order to prevent the value from getting "stepped on" it first creates a new memory location to store the value, then continues processing what is still in the register. In this case, it increments i after the new location has been created.
This is how it would operate if precedence is to work properly and you had further operations that were lower priority than assignment. Make sense?No.
Whenever we have LHS = RHS; RHS is evaulated completely and the value of the RHS expression is then stored in the LHS variable. In the case of i = i++; we first evaluate the i++, which has the side effect of incrementing i. Then the value of the expression i++ is stored in the LHS--in i.
Since the value of i++ is i's original value (Remember, the post-increment operator increments the variable after getting its current value), that's what's stored in the LHS as a result of the assignment.
int i = 1;
i = i++;
// is equivalent to
int i = 1;
tmp = i; // get original value of i as the value of the expression i++, tmp = 1
i = i + 1; // increment i, i = 2
i = tmp; // this is the "i = " part