& <-- verifies both operands
&& <-- stops evaluating if the first operand evaluates to false since the result will be false
(x != 0) & (1/x > 1)
<-- this means evaluate (x != 0)
then evaluate (1/x > 1)
then do the &. the problem is that for x=0 this will throw an exception.
(x != 0) && (1/x > 1)
<-- this means evaluate (x != 0)
and only if this is true then evaluate (1/x > 1)
so if you have x=0 then this is perfectly safe and won't throw any exception if (x != 0) evaluates to false the whole thing directly evaluates to false without evaluating the (1/x > 1)
.
EDIT:
exprA | exprB
<-- this means evaluate exprA
then evaluate exprB
then do the |
.
exprA || exprB
<-- this means evaluate exprA
and only if this is false
then evaluate exprB
and do the ||
.
Besides not being a lazy evaluator by evaluating both operands, I think the main characteristics of bitwise operators compare each bytes of operands like in the following example:
int a = 4;
int b = 7;
System.out.println(a & b); // prints 4
//meaning in an 32 bit system
// 00000000 00000000 00000000 00000100
// 00000000 00000000 00000000 00000111
// ===================================
// 00000000 00000000 00000000 00000100
boolean a, b;
Operation Meaning Note
--------- ------- ----
a && b logical AND short-circuiting
a || b logical OR short-circuiting
a & b boolean logical AND not short-circuiting
a | b boolean logical OR not short-circuiting
a ^ b boolean logical exclusive OR
!a logical NOT
short-circuiting (x != 0) && (1/x > 1) SAFE
not short-circuiting (x != 0) & (1/x > 1) NOT SAFE
It depends on the type of the arguments...
For integer arguments, the single ampersand ("&")is the "bit-wise AND" operator. The double ampersand ("&&") is not defined for anything but two boolean arguments.
For boolean arguments, the single ampersand constitutes the (unconditional) "logical AND" operator while the double ampersand ("&&") is the "conditional logical AND" operator. That is to say that the single ampersand always evaluates both arguments whereas the double ampersand will only evaluate the second argument if the first argument is true.
For all other argument types and combinations, a compile-time error should occur.
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