Boolean | vs Logical ||?

Question

First of all, I know this won't work for bitwise |.
But, this code:
boolean a=false, b=true, c;
c = a|b; // c is now true
c = a||b; // c is now also true
Is it just a remnant from the C-style language, or what?
Are boolean | and logical || optimized differently?
Conditions in Java can only evaluate to boolean values, so things like this
if ((a == false) | (b == false))
works just as well as
if ((a == false) || (b == false))
I'd say it's bad style to use || for boolean (as in c=a||b;), but does it really matter?
-- Tino Didriksen, [email protected]

Answer 1

| is a bitwise OR that operates on integral types (char, short, int, long), and apparently, boolean.
|| is a boolean or logical OR that operates on boolean.
| evaluates to an integral values (I don't know if it's int or the larger of the operand types, or what).
A || B can short circuit because the truth of the entire statement is known if A is true.
x | y cannot, in general, short circuit, because it's a bitwise or--that is, you have to examine each bit. Now you COULD examine only those bits of y for which the corresponding x bit was 0, and then if x was all 1s, not examine y at all. However, Java doesn't work this way, AFAIK--it just operates on all values as the general case--examining both operands.
It's been put forth that the difference between | and || is that | doesn't short circuit and || does. I would say that's a side effect. The real fundamental difference is that | does bitwise operations on integral operands to produce an integral result, whereas || does a boolean operation on boolean operands to produce a boolean result.
The comparisons using true/false stem from the fact that, for | (and I assume &), boolean expressions (e.g. true/false) seem to be treated as single bit integral types. However, in the general case, boolean and integral types are not interchangeable in Java, and the issues of short circuit vs. not doesn't apply, since the two operators do different things and operate on different types.