Why swapping integer variable by XOR doesn't work in a single line?

Question

I want to swap the value of two integer variables in java using the XOR operator.

This is my code:

int i = 24;
int j = 17;

i ^= j;
j ^= i;
i ^= j;

         


        

Answer 1

By writing your swap all in one statement, you are relying on side effects of the inner i ^= j expression relative to the outer i ^= (...) expression.

From the Java specificiation (15.26 Assignment Operators):

There are 12 assignment operators; all are syntactically right-associative (they group right-to-left). Thus, a=b=c means a=(b=c), which assigns the value of c to b and then assigns the value of b to a.

[...]

AssignmentOperator: one of = *= /= %= += -= <<= >>= >>>= &= ^= |=

You might want to consider the readability of the code. Perhaps it's best to e.g. put the code in a method called swap(), or do the actual swapping through the use of a temp variable:

int temp = i;
i = j;
j = temp;