Labeled "break" Statements

Java Tutorials - Herong's Tutorial Examples

∟Labeled "break" Statements

This section describes labeled 'break' statement, which is a branching statement that transfers the control to the end of the labeled enclosing block statement.

What Is Labeled "break" Statement? - A labeled "break" statement is a branching statement that transfers the control to the end of the labeled enclosing block statement.

Here is the syntax for a labeled "break" statement.

block_label : ... {
   ...
   {
      ...
      break block_label
      ...
   }
   ...
}
// break continue here

Labeled "break" statements extend usages of non-labeled "break" statements in 2 situations:

Break block statements other than "switch", "while", "do", or "for" statements.
Break a parent block statement of the immediate enclosing block statement.

Here is a sample program that shows you how to use labeled "break" statements:

/* LabeledBreakStatementTest.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
class LabeledBreakStatementTest {
   public static void main(String[] arg) {
      java.io.PrintStream out = System.out;

      out.println("\"break\" statement in a dummy block:");
      blockDummy : {
         out.println("   One");

         if (true) break blockDummy;
         out.println("   Two");
      }
      out.println("   Three");

      out.println("\"break\" statement in an \"if\" block:");
      blockIf : if (true) {
         out.println("   Monday");

         if (true) break blockIf;
         out.println("   Tuesday");
      }
      out.println("   Wednesday");

      out.println("\"break\" statement in a two-level block:");
      boolean isPrime;
      int i = 3;
      int operations = 1;

      blockOuter: while (true) { // block level 1
         isPrime = true;
         int j = 2;

         blockInner : while (j < i) { // block level 2
            isPrime = i%j > 0;

            if (!isPrime) break blockInner;
            j++;

            if (operations > 100) break blockOuter;
            operations++;
         }

         if (isPrime) out.println("   "+i+" is a prime number.");
         i++;
      }
   }
}

If you compile and run the above program, you will see:

herong> java LabeledBreakStatementTest.java

"break" statement in a dummy block:
   One
   Three

"break" statement in an "if" block:
   Monday
   Wednesday

"break" statement in a two-level block:
   3 is a prime number.
   5 is a prime number.
   7 is a prime number.
   11 is a prime number.
   13 is a prime number.
   17 is a prime number.
   19 is a prime number.
   23 is a prime number.