Behavior of &&
public class BusinessRulesTrab212 {
public int Save(int newcod, String obs)
throws ClassNotFoundException, SQLException {
// DataAccessTrab212 t = new DataAccessTrab212();
return 1 // t.Insert(newcod, obs);
}
}
--
and ...
BusinessRulesTrab212 t = new BusinessRulesTrab212();
boolean r = false;
r &&= (t.Save(newcod, obs) == 1);
--
Java dont call the function Save from Object t, and allways r gets a value of false. Why this code doesnt work?.
[537 byte] By [
gescobara] at [2007-10-2 6:25:05]
r &&= (t.Save(newcod, obs) == 1);
I never knew you could do &&= but if it compiles, I guess it's equivalent to r = r && whatever;
Now, since you initialize r to false, it's equivalent to r = false && whatever;
false && anything is always false.
&& is the logical AND operator. Java will stop evaluating results as soon as it encounters a single false value. Because your r value is false and it is on the left hand side, it is evaluated first, and that will always cause the && to fail, so it doesn't even bother with the right hand side of the operation.
> doh, too slow
But you did add the important point that t.Save() will never get called due to th short-circuit boolean.
@OP: If you wanted t.Save() to be called even if the LHS of the AND was false, you could use & instead of &&. && short-circuits, but & always evaluates both sides.
Note that r = false & whatever will still leave r false though.
