I have some switch statement as shown below. Notice there is no break. Findbugs is reporting error on the second case statement only. The error is : Switch statement found where one case falls through to the next case.
switch(x) {
case 0:
// code
case 1:
// code
case 2:
// code
}
Findbugs is flagging up that falling through from one case
to the next is generally not a good idea if there's any code in the first one (although sometimes it can be used to good effect). So when it sees the second case
and no break
, it reports the error.
So for instance:
switch (foo) {
case 0:
doSomething();
case 1:
doSomethingElse();
default:
doSomeOtherThing();
}
This is perfectly valid Java, but it probably doesn't do what the author intended: If foo
is 0
, all three of the functions doSomething
, doSomethingElse
, and doSomeOtherThing
run (in that order). If foo
is 1
, only doSomethingElse
and doSomeOtherThing
run. If foo
is any other value, only doSomeOtherThing
runs.
In contrast:
switch (foo) {
case 0:
doSomething();
break;
case 1:
doSomethingElse();
break;
default:
doSomeOtherThing();
break;
}
Here, only one of the functions will run, depending on the value of foo
.
Since it's a common coding error to forget the break
, tools like Findbugs flag it up for you.
There's a common use-case where you have multiple case
statements in a row with no intervening code:
switch (foo) {
case 0:
case 1:
doSomething();
break;
case 2:
doSomethingElse();
break;
default:
doSomeOtherThing();
break;
}
There, we want to call doSomething
if foo
is 0
or 1
. Most tools won't flag this up as a possible coding error, because there's no code in the case 0
prior to the case 1
and this is a fairly common pattern.