There is a bug in CopyOnWriteMap

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

Start by locating the Java CopyOnWriteMap implementation and inspect CopyOnWriteMap.entrySet(), especially how its iterator handles remove(). Compare the intended behavior with CopyOnWriterArrayList and the referenced implementation at src/main/java/cn/yxffcode/freetookit/collection/CopyOnWriterMap.java; done means iterator removal cannot mutate the underlying map unexpectedly.

Written by the indexing model from the issue text.