L2J Server

they all both thread safe。
am I right？

Yes but FastMap is sorted its like a thread-safe LinkedHashMap

Nos wrote:Yes but FastMap is sorted its like a thread-safe LinkedHashMap

FastMap is sorted by insert order, the other "thread-safe" sorted map is ConcurrentSkipListMap which is sorted by natural order of keys.

Also FastMap is concurrent, and does not imply thread-safe, unless specified calling shared.