Cyclicbarrier and countdownlatch [concurrent programming]

1.CyclicBarrier A brief overview of

CyclicBarrier It is a synchronization tool class for multiple threads waiting for each other to reach a common barrier point , Here's the picture , Xiao Ming , Xiaobao , Xiao Zhou needs to wait for others to reach the public barrier point , To continue to do other things , It is often used for tasks that need to be completed by multiple threads . The essence is through Lock, Control one state state , Atomic update to 0.

CyclicBarrier Literally means “ Reusable fence ”,CyclicBarrier comparison CountDownLatch Come on , It's a lot easier , Its source code does not have what deep place , It is ReentrantLock and Condition Combined use of .
CyclicBarrier and CountDownLatch Is it very similar , It's just CyclicBarrier There can be more than one fence , Because of its fence （Barrier） Can be reused （Cyclic）.

2.CyclicBarrier Two scenarios used

1、n Threads have prepared some data , And then call await Method , The main thread is handled by them , It can be summed up n Data prepared by threads .

2、n All threads are waiting , One by one ,await The method is equivalent to checking in , Every thread calls await Sign in first , Wait until the number of barriers equals 0, Then deal with the following logic , The thread that finally signed in executes the barrier and wakes up other waiting threads .

3.CyclicBarrier And CountDownLatch difference

1、CyclicBarrier Can be reset , and CountDownLatch Cannot reset .

2、CountDownLatch Is the count of one or more threads reduced to 0, Start doing things together .CyclicBarrier Is the last thread , Wake up other counter is 0 The thread of , Start doing things .

3、CyclicBarrier It's based on exclusive locks ReentrantLock Exclusive lock implementation ,CountDownLatch It is based on shared lock .