How to share the objects safely ?

POLICIES FOR SHARING OBJECT

Thread confined object

owned exclusively by one thread and can be modified by its owning thread.

Shared Read-only object

can be accessed concurrently by multiple threads but cannot be modified by any thread.

(Immutable and Effectively immutable objects)

Shared Thread-safe object

performs synchronization internally and multiple threads can access / modify

Guarded object

can be accessed only with a specific lock held.

These are encapsulated within other thread-safe objects.