java operator and exclusive with boolean operands

Question

can anyone tell me why it prints out 1? I know for sure that true and false AND EXCLUSIVE gives 0. why it enters in if statement?

 public static void main(String[] args) { boolean a=true, b=false; int i=0; if(a^b) { i++; } System.out.print(i++); }

thank you!

Community · Accepted Answer · 2017-05-23 10:25:07Z

5

You're using xor : ^.

true ^ false == true

3 Comments

But I learnt that XOR gives true only when we have 1 and 1 (true , true) , but in this case we have 1 and 0 (false). isn't?

That's just "AND". As in && or &

T && T == T, T && F == F, T ^ T == F, T ^ F == T

Stephen Connolly · Accepted Answer · 2013-06-17 13:30:03Z

xor tables

0^0 == 0 0^1 == 1 1^0 == 1 1^1 == 0

So it enters the if statement.

At the end of your main block, after the System.out.println(i++) the i variable will have the value 2 as currently written

fge · Accepted Answer · 2013-06-17 13:29:23Z

If you talk about ^, it is exclusive or. And for any propositions p1 and p2, p1 ^ p2 is true only if one of p1 or p2 are true.

It is therefore normal that it prints 1.

manub · Accepted Answer · 2013-06-17 13:30:13Z

In Java the ^ operator is bitwise Exclusive OR, not Exclusive AND. Since true XOR false is TRUE, it enters in the if clause.

I'd suggest for you simply to use == and != operators, if you're dealing with boolean.

In this context it is not the bitwise exclusive or, but the logical exclusive or ;)

Anders R. Bystrup · Accepted Answer · 2013-06-17 13:47:24Z

The ^ operator is exclusive or. The truth table for this is

 XOR | false true ------------------- false | false true true | true false

That's why you get "1" - your if statement evaluates to true.

Cheers,