Thanks for your message, I'm aware of the compatibility issue.
However the library should be binary compatible, so
basically usage should be possible.
You can get compile errors if you try to compile your application with Java 21.
There is an issue with reversed() which can however be mitigated with an explicit cast, see example below.
Can you give me more information which issues you faced and why you had to revert to ArrayList?
void testBrowniesCollectionsJava21() {
IList<String> strs = GapList.create("abc", "def");
// Compiler error
//List<String> strs2 = strs.reversed();
// Ok
List<String> list = ((List<String>) strs).reversed();
Deque<String> deque = ((Deque<String>) strs).reversed();
}