The Eclipse Java Compiler (which is used as a replacement for Sun's java in java-gcj) issues many ominous warnings on unnecessary imports, unused members and serializable classes missing serializationUID. All of these issues appear cosmetic, but should be cleaned up.
Committed revs 533199, 533200 and 533215 to kill a lot but not all of them. Most of the remaining are in lf5 and chainsaw 1.