Beware when you're creating URL instances by providing the entire spec without separating it into protocol, host, and file.

If your URL spec happens to be in the following format:

file://C:/somepath/file

JDK 1.4 will try to lookup the C host name. This will of course fail, but by default it takes 5 minutes to do so on Windows. Imagine what happens when you have several of these URLs ...

To work around this issue, make sure to instantiate your file protocol URLs like this:

String filepath = "C:/somepath/file";
URL url = new URL("file", null, filepath);

This will prevent the JDK from getting confused.

You can find proof of this behavior in this screenshot of a debugging session that Stéphane Meslin-Weber performed to track down slow startup times in RIFE:

This issue seems to have been fixed in JDK 1.5.

Update:

It seems that I jumped to conclusions too quickly and that the correct URL format should have an additional slash:

file:///C:/somepath/file

The confusing part for us was that JDK 1.5 doesn't seem to try to lookup C as a hostname, which made the issue very hard to track down since none of the core RIFE devs use JDK 1.4. We use retroweaver to generate a compatible version.