Breaking Loops

There are two kinds of breaks for a loop:

The unlabeled break: break;
The labeled break: break label;

What you must know about the unlabeled break is:

It terminates the innermost switch, for, while, or do-while
You get a compiler error if not one of these loops encloses the break statement

And what you must know about the labeled break is:

It terminates the labeled statement (any, not only loops)
The control flow is transferred to the statement immediately following the labeled (terminated) statement or block
It’s valid only within the block of code under the scope of the label

Below you have a couple of labeled break examples:


  // Example 1: break a block
  block : { 
     // … code here
     break block; 
     // … more code here
  }
  next_statement_after_break;

  // Example 2: break nested statements
  label1:
     for (i = 0; i < 9; i++) {
         for (j = 0; j < 9; j++) {
            if (i == j) {
               break label1;
            }
         }
      }
  next_statement_after_break;

// Example 1: break a block

block : {

// … code here

break block;

// … more code here

}

next_statement_after_break;

// Example 2: break nested statements

label1:

for (i = 0; i < 9; i++) {

for (j = 0; j < 9; j++) {

if (i == j) {

break label1;

}

next_statement_after_break;

Finally, remember that you can also break the execution flow using the return reserved word to exit from the current method: return; for void methods or return expression; for non-void methods.

Continuing Loops

There are also two ways to continue (skip the current iteration) a loop:

The unlabeled continue: continue;
The labeled continue: continue label;

What you must know about the unlabeled continue is:

It skips the current iteration of a for, while, or do-while loop
It skips to the end of the innermost loop’s body and evaluates the boolean expression that controls the loop
You get a compile-time error if either:
- No for, while or do statement encloses the continue
- The continue target (label) is not a for, while or do

And what you must know about the labeled continue is that it’s exactly as the unlabeled one (same considerations) but in this case it skips the current iteration of an outer loop marked with the given label.

Below you have a couple of continue examples:


  // Example 1: unlabeled continue (it prints 1 and 2)
  for (int i = 0; i < 3; i++) {
     if (i == 0) 
        continue;
     else
        System.out.println(i);
  }

  // Example 2: labeled continue (it prints nothing)
  label1:
     for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
           if (j == 0) 
             continue label1;
           else
             System.out.println(j);
        }
     }

// Example 1: unlabeled continue (it prints 1 and 2)

for (int i = 0; i < 3; i++) {

if (i == 0)

continue;

else

System.out.println(i);

}

// Example 2: labeled continue (it prints nothing)

label1:

for (int i = 0; i < 3; i++) {

for (int j = 0; j < 3; j++) {

if (j == 0)

continue label1;

else

System.out.println(j);

}

Loops: break and continue

Breaking Loops

Continuing Loops

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