“loop:” in Java code. What is this, and why does it compile?

Question

This code just made me stare at my screen for a few minutes:

loop:
for (;;) {
    // ...
}

(line 137 here)

I have never seen this b

Answer 1

It is a label, and labels in Java can be used with the break and continue key words for additional control over loops.

Here it is explained in a rather good way:

Thinking in Java, break and continue