CODEWITHSUNDEEP
javalabelbreak
AmViL
AmViL

Reputation: 3

Break from other class possible?

I recently rediscovered the use of breaking back to a label. Now I'm wondering if it is possible to break back to a label from another class.

Example of what i want:

Main.class

label:
for (Product p : ProductList) {
 if (p.getSet() == true) {
  classHandler();
 }
}

Classhandler.class

someFunction() {
 break label;
}

While I was typing this I actually tried making a local function in my Main class (so I could just call that function instead) but even there I got the undefined label: label error.

Upvotes: 0

Views: 791

Answers (4)

Heiko Schmitz
Heiko Schmitz

Reputation: 330

It doesn't make sense, since there is no guarantee that label exists, not even that someFunction() is called within a loop.

Upvotes: 0

Thilo
Thilo

Reputation: 262842

No, you cannot. That does not even work between two methods of the same class. Labels are scoped (at the most) within a single method.

Upvotes: 0

ditkin
ditkin

Reputation: 7054

The label that you break to must be in scope. From the java sun documentation:

A break statement with label Identifier attempts to transfer control to the enclosing labeled statement (§14.7) that has the same Identifier as its label; this statement, which is called the break target, then immediately completes normally. In this case, the break target need not be a while, do, for, or switch statement. A break statement must refer to a label within the immediately enclosing method or initializer block. There are no non-local jumps

Upvotes: 1

Joachim Sauer
Joachim Sauer

Reputation: 308269

No, you can't. And you shouldn't.

If the condition for breaking is some problem, then throwing an exception would be the correct approach.

Otherwise you should do something like returning a flag that indicates if other products should still be handled and reacting on that in your loop.

As you noticed you can't even break through method-borders, and that's a good thing. break and continue are powerful tools, but can easily make your code confusing, if used in the wrong way. For example a break hidden inside a huge code block can be easy to miss, but if you use a continue at the very top of a method to skip an iteration based on some condition, then the intention is pretty clear.

Upvotes: 5

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