Java Reference
In-Depth Information
The labeled
break
enables you to break out to the statement following an enclosing block or loop that has
an identifying label, regardless of how many levels of nested blocks there are. You might have several loops
nested one within the other, for example, where you could use the labeled
break
to exit from the innermost
loop (or indeed any of them) to the statement following the outermost loop. You just need to add a label to
the beginning of the relevant block or loop that you want to break out of, and use that label in the
break
statement.
Just to see it working you can alter the previous example to use a labeled
break
statement:
public class Primes4 {
public static void main(String[] args) {
int nPrimes = 50; // The maximum number of primes required
// Check all values from 2 to nValues
OuterLoop:
for(int i = 2 ; ; ++i) { // This loop runs forever
// Try dividing by all integers from 2 to i-1
for(int j = 2; j < i; ++j) {
if(i % j == 0) { // This is true if j divides exactly
continue OuterLoop; // so exit the loop
}
}
// We only get here if we have a prime
System.out.println(i); // so output the value
if(--nPrimes == 0) {
// Decrement the prime count
break OuterLoop;
// It is zero so we have them all
}
}
// break OuterLoop goes to here
}
}
The program works in exactly the same way as before. The labeled
break
ends the loop operation begin-
ning with the label
OuterLoop
, and so effectively branches to the point indicated by the comment.
