- Is breaking and continuing the only uses of labeled statements in Java?
- When have you used Labeled Statements in your programs?
Sorry the code snippet has been deleted. I am splitting the question
Sorry the code snippet has been deleted. I am splitting the question
Yes,
break
andcontinue
are the only two uses for labeled statements in Java. (Java has nogoto
statement.)You can use a label to break out of nested loops.
When you
continue
back to theouter
label, you're skipping the remainder of both the inner and the outer loop, including the print statement.JLS 14.7 Labeled statements
(edited for clarity)
So the JLS is clear that labels are used with
break
orcontinue
, and no other grammatical element of the Java programming language uses it.Strictly speaking,
break
andcontinue
, labeled or not, are NEVER necessary. They can always be written out of the code. Used idiomatically, however, they can lead to more readable code.Here's an illustrative example: given an
int[]
, we want to :"One (1)"
on1
"Two (2)"
on2
"Zero "
on0
immediately stop processing on any other number
Here we see that:
switch
break
in theswitch
is used to avoid "fall-through" between casescontinue loop;
is used to skip post-processing oncase 0:
(the label is not necessary here)break loop;
is used to terminate the loop ondefault:
(the label is necessary here; otherwise it's aswitch break
)So labeled
break
/continue
can also be used outside of nested loops; it can be used when aswitch
is nested inside a loop. More generally, it's used when there are potentially multiplebreak
/continue
target, and you want to choose one that is not immediately enclosing thebreak
/continue
statement.Here's another example:
Here's another case of a labeled
break
being used not within an iterative statement, but rather within a simple block statement. One may argue that the labels lead to better readability; this point is subjective.And no, the last line DOES NOT give compile time error. It's actually inspired by Java Puzzlers Puzzle 22: Dupe of URL. Unfortunately, the puzzle does not go into "proper" use of labeled statements in more depth.