Comment by nl

You'd think that is so completely wrong that no competent programmer would ever do it...

Except the java.net.URL.equals and java.net.URL.hashcode methods do almost the same thing: they issue DNS requests (!)

"Two hosts are considered equivalent if both host names can be resolved into the same IP addresses; else if either host name can't be resolved, the host names must be equal without regard to case; or both host names equal to null."

See https://docs.oracle.com/en/java/javase/11/docs/api/java.base...

There is a bug raised[1], but it can't be fixed for backwards compatibility reasons.

I'll never forget this now, after debugging a very horrible and severe and very intermittent performance issue in some code over 20 years ago. A (slow) DNS resolver occasionally caused 1000x performance degradation on remote sites. That was horrible to work out.

[1] https://bugs.java.com/bugdatabase/view_bug.do?bug_id=4434494