Java Reference
In-Depth Information
The
break
and
continue
Statements
★
In previous subsections, we described the basic flow of control for the
while
,
do-while
, and
for
loops. This is how the loops should normally be used and they are
usually are. However, you can alter the flow of control in two additional ways: You can
insert either a
break
statement or insert a
continue
statement. The
break
statement
ends the loop. The
continue
statement ends the current iteration of the loop body.
The
break
and
continue
statements can be used with any of the Java loop statements.
We described the
break
statement earlier in this chapter when we discussed the
switch
statement. The
break
statement
consists of the keyword
break
followed by a
semicolon. When executed, the
break
statement ends the nearest enclosing
switch
or
loop statement.
The
continue
statement
consists of the keyword
continue
followed by a
semicolon. When executed, the
continue
statement ends the current loop body
iteration of the nearest enclosing loop statement.
One point that you should note when using the
continue
statement in a
for
loop is that the
continue
statement transfers control to the update expression. Thus,
any loop control variable will be updated immediately after the
continue
statement
is executed.
Note that a
break
statement completely ends the loop. In contrast, a
continue
statement merely ends one loop iteration, and the next iteration (if any) continues
the loop.
You never absolutely need a
break
or
continue
statement. Any code that uses
a
break
or
continue
statement can be rewritten to do the same thing without a
break
or
continue
statement. The
continue
statement can be particularly tricky
and can make your code hard to read. It may be best to avoid the
continue
statement
completely or at least use it only on very rare occasions. The use of the
break
and
continue
statements in loops is controversial, with many experts saying they should
never be used. You will need to make your own decision on whether you will use either
or both of these statements.
You can nest one loop statement inside another loop statement. When doing
so, remember that any
break
or
continue
statement applies to the innermost loop
statement containing the
break
or
continue
statement. If there is a
switch
statement
inside a loop, any
break
statement applies to the innermost loop or
switch
statement.
There is a type of
break
statement that, when used in nested loops, can end any
containing loop, not just the innermost loop. If you label an enclosing loop statement
with an
Identifier
, then the following version of the
break
statement will exit the
labeled loop, even if it is not the innermost enclosing loop:
break
statement
continue
statement
break
Identifier
;
label
To
label
a loop statement, simply precede it with an
Identifier
and a colon. The
following is an outline of some sample code that uses a labeled
break
statement:
outerLoop:
do
