multithreading - What is purpose of Read Lock in java synchronization -

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i new in multithreading , confused , why read lock needed in java synchronization .also understand use case of write lock.in scenario need limit reader access threads. suppose don't have read lock in java , what's problem.

suppose there shared resource r. thread t1 reading , it's not locked there no read lock in java(as said)meanwhile second thread try access r1 write on it. there in no information attached r1 thread read , second thread write lock , start writing not aspected. read lock information attached resource tell later threads resource in access reading , wait write access or can access read. read lock can access multiple thread.


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