i=i++ and s=i++

[alpa urja]

anybody explain me why output like that?
1.class Test{
public static void main(String args[])
{
int i=0;
i=i++;
System.out.println(i);//0
i=i++;
System.out.println(i);//0
i=i++;
System.out.println(i);//0
}
}

2.class Test{
public static void main(String args[])
{
int i=0,s;
s=i++;
System.out.println(i);//1
s=i++;
System.out.println(i);//2
s=i++;
System.out.println(i);//3
}
}

[sasi dhulipala]

Hi,
This is something to do with operator precedence.
First to be eveluated is ++ and last to be evaluated is =
the assignment operator.
let us take the case of
i = i++;
since = has least precedence the RHS ( Right Hand Side ) expression is to be evaluated first.
which is i++; here first it returns the val if i ( i == 0 ) first and then increments i to i+1 i.e i =1 ;
and finally when it is evaluating '=' operator it assigns zero to i; so i finally becomes zero ( i == 0 )
Now this set of statements are repeated thrice in the code
and each time i is set to zero and hence it prints zero three times
coming to the case of s = i ++;
proceding similarly after first statement s = 0 and i =1
here i is not reset to zero as it is assigned to a different variable.
continuing similarly the after the second s = i++;
s = 1 and i = 2;
after third s = 2 and i = 3;
HTH
Sasidhar


[This message has been edited by sasi dhulipala (edited January 04, 2001).]

[Kirti Singh]

there are 2 things
1. ++ operator has precedence over = operator
2. i++ returns i and increases the value of i by 1
therefore i=i++ would set the value of i on the left hand side to i not i+1
and s=i++ would set s=i and i to i+1.
K Singh