Presumably these are event listeners are added by the user of the library? as opposed to JSword internally using them? Obviously, we only want to do this if it's rarely used - as copying a list of stuff many times would result in un-necessary memory allocations if it were use many times during an operation.

Otherwise, all up for reducing complexity. I'd personally favour waiting for Java 6 and use http://docs.oracle.com/javase/6/docs/api/java/util/concurrent/ConcurrentLinkedQueue.html

What do you think?

The EventListenerList is used in a dozen places in JSword to manage listeners of a single type per list.
Every time any action is done on the list, a copy of the list is made.

Moving to CopyOnWriteArrayList is a significant performance improvement as it only does a copy on write. I've been running with it as the listener list in the Progress meter and it has solved the synchronization deadlock (which I thought I solved earlier, but merely minimized it) and I can index Bibles faster than I can get to the next. Before the change, I could stack a half dozen or so.

The big gain is that the listener lists seldom change. So it is almost like using an unsynchronized list.

I discovered the usage when researching synchronization problems for listener lists.

So, I'd rather not wait. The choice right now is either leaving EventListenerList or use CopyOnWriteArrayList. We can certainly revisit when we get to Java 6.

Sounds good Let's go for it.