There is a bug in CopyOnWriteMap

[gaohanghbut]

CopyOnWriteMap.entrySet() cannot simply delegate to map.entrySet() because we can use entryset.iterator().remove() method to remove elements from the map.As an example,the CopyOnWriterArrayList not allow to use iterator to remove elements.

After read your code, I implemented the CopyOnWriteMap, maybe it is better:
https://github.com/gaohanghbut/freetookit/blob/master/src/main/java/cn/yxffcode/freetookit/collection/CopyOnWriterMap.java