About labels in Java behaving like GOTOs

Question

Shouldn't this loop infinitely?

someLabel:{
        for (int i = 0; i < 5; ++i) {
            System.out.println(i);
            if (i == 3)
                break someLabel;
        }
}

It goes

Then dies. I was reading a question about an alternative to GOTO in Java. This was the accepted answer: https://stackoverflow.com/a/2430789/555690. Shouldn't the for loop be executed again?

that `break` will "break" the code block, it is not like a `continue` inside a for/while loop — morgano, Jul 03 '14 at 02:22

score 1 · Answer 1 · answered Jul 03 '14 at 02:30

From http://docs.oracle.com/javase/tutorial/java/nutsandbolts/branch.html:

The break statement terminates the labeled statement; it does not transfer the flow of control to the label. Control flow is transferred to the statement immediately following the labeled (terminated) statement.

Apart from the fact that I never saw any real code using this kind of control flow, I guess a use for it would be to break an outer loop from an inner loop (as described in the provided link):

search:
    for (i = 0; i < arrayOfInts.length; i++) {
        for (j = 0; j < arrayOfInts[i].length;
             j++) {
            if (arrayOfInts[i][j] == searchfor) {
                foundIt = true;
                break search;
            }
        }
    }

score 0 · Answer 2 · answered Jul 03 '14 at 02:28

The Java language specification states

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.

The statement here is actually a block statement. Once you break, that block ends.

So, no, the for loop should not iterate again since it's inside the block that just ended.

About labels in Java behaving like GOTOs

2 Answers2