Java tags? Outer, middle, inner

Please don't worry about loops, but my question is about those keywords: external, intermediate and internal They are not declared as instance variables. Why does the IDE let the code compile? I did some searches on Google. Is this the Java tag? Some keyword in Java? Thank you very much

public class LoopTest{

public static void main(String[] args){
    int counter = 0;

    outer:
    for(int i = 0; i < 3; i++){
        middle:
        for(int j = 0; j < 3; j++){
            inner:
            for(int k = 0; k < 3; k++){{            
            }
                if(k - j > 0){
                    break middle;
                }
                counter++;
            }
        }
    }
    System.out.println(counter);
}

}

Solution

Java support tags This is described in this article from Oracle

So basically, you can have a loop with labels. You can use the keywords continue, break, etc. to control the flow of the loop

The following example illustrates how to use a loop with the break keyword When break is called, it terminates the marked statement, that is, the statement after somelabel

someLabel:
    for (i = 0; i < 100; i++) {
        for (j = 0; j < 100; j++) {
            if (i % 20 == 0) {
                break someLabel;
            }
        }
    }

The continue keyword handles labels in the same way When you call, for example, continue some tags; The external circulation will continue

As per this so question, you can also do the following structure:

BlockSegment:
if (conditionIsTrue) {
    doSomeProcessing ();
    if (resultOfProcessingIsFalse()) break BlockSegment;
    otherwiseDoSomeMoreProcessing();
    // These lines get skipped if the break statement
    // above gets executed
}
// This is where you resume execution after the break
anotherStatement();

Personally, I would never recommend labels Conversely, if you rearrange your code so that you don't need labels (such as breaking complex code into smaller functions), I'll find it easier to understand