“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

This is really a reply to seanizer's comment on org.life.java's answer, but I wanted to put in some code so I couldn't use the comment feature.

While it is very rare that I find a use for "break label", it does happen occassionally. The most common case is when I am searching for something that is in a structure requiring a nested loop to search, like:

search:
for (State state : stateList)
{
  for (City city : state.cityList)
  {
    if (city.zipcode.equals(wantZip))
    {
      doSomethingTo(city);
      break search;
    }
  }
}

Usually in such cases I push the whole thing into a subroutine so that on a hit I can return the found object, and if it falls out the bottom of the loop I can return null to indicate a not found, or maybe throw an exception. But this is occasionally useful.

Frankly, I think the inventors of Java included this feature because between this and exception handling, they eliminated the last two legitimate uses for GOTO.

Very late addendum:

I saw a great gag line of code once. The programmer wrote:

http://www.example.com/xyz.jsp
for (Foo foo1 : foolist)

He didn't actually say "example.com" but our company's web site.

It gives the impression that there's a URL in the code. It compiles successfully, like it does something. But ... what does it do?

In reality it does nothing. "http:" is a label that he never references. Then the "//" makes the rest of the line a comment.