Usage of countdownlatch

Try to solve a problem today , Is in the Android Realize multithread synchronization in , But it requires several variables to be synchronized at the same time .

at that time , The first thing to think about is , It must be used Android or JAVA Its own mechanism .

I found a man named CountDownLatch The mechanism of .

CountDownLatch Multithreaded synchronization class , It can coordinate the synchronization between multiple threads .

CountDownLatch The typical usage of is as follows ：

1） Create a CountDownLatch example , And determine the number of threads or tasks that need to wait ;

2） A thread or task completes ,CountDownLatch Counter minus one ;

3） Use CountDownLatch.await(), etc. CountDownLatch The counter of is 0, Then run .

CountDownLatch There are three important methods in the class

// Constructors , Set the number of reference counts 
public CountDownLatch(int count){}
// call await() Method will be suspended , It will wait until count The value is 0 To continue 
public void await() throws InterruptedException { };   
// and await() similar , Just wait for a certain time count Value hasn't changed to 0 It will continue 
public boolean await(long timeout, TimeUnit unit) throws InterruptedException { };  
// take count Value reduction 1
public void countDown() { };

Using this method , Sure enough, the problem was solved .

Note appended ：

CountDownLatch and CyclicBarrier The difference between ：

1）CountDownLatch It's a counter , Counter decrement , Until used up ; You must reconstruct or assign values if you want to use ;

2）CyclicBarrier The counter is like a valve , Until all threads arrive , Can be done reset And use it many times .