What is the purpose of Key Annotation annotation?

1.	What is the purpose of Key Annotation annotation?
Answer» This annotation sets the Key for type conversion. The Key annotation must be applied at field or method level. Key( value = java.lang.Long.class )private Map<Long, User> userMap;

Answer»

This annotation sets the Key for type conversion. The Key annotation must be applied at field or method level.

Key( value = java.lang.Long.class )private Map<Long, User> userMap;

Discussion