CyclicBarrier(同步容器)
作用
它允许一组线程相互等待直到所有线程都到达一个公共的屏障点,才开始执行下面的操作，举例：例如做公交车，等所有人都坐上车了，车才启动出发
方法
public CyclicBarrier(int parties);
public CyclicBarrier(int parties, Runnable barrierAction);
private void nextGeneration();
private void breakBarrier();
private int dowait(boolean timed, long nanos)
throws InterruptedException, BrokenBarrierException,
TimeoutException;
public int getParties();
public int await() throws InterruptedException, BrokenBarrierException;
public int await(long timeout, TimeUnit unit)
throws InterruptedException,
BrokenBarrierException,
TimeoutException;
public boolean isBroken();
public void reset();
public int getNumberWaiting();
示例
不设定阻塞时间
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* @author scottxuan
*/
@Slf4j
public class CyclicBarrierExample1 {
//线程数
private final static int threadNum = 4;
//初始化线程同步数量
final static CyclicBarrier barrier = new CyclicBarrier(2);
public static void main(String[] args) throws InterruptedException {
ExecutorService service = Executors.newCachedThreadPool();
for (int i = 0; i < threadNum; i++) {
final int num = i;
service.execute(()->{
update(num);
});
Thread.sleep(500);
}
service.shutdown();
}
public static void update(int num){
try {
log.info("thread ready {}",num);
//线程阻塞
barrier.await();
log.info("thread continue {}",num);
} catch (Exception e) {
e.printStackTrace();
}
}
}
//输出结果 4个线程 同步数为2 2个线程就绪 阻塞释放 开始执行await()后续代码
//01:48:07.213 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread ready 0
//01:48:07.715 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread ready 1
//01:48:07.715 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread continue 1
//01:48:07.715 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread continue 0
//01:48:08.221 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread ready 2
//01:48:08.736 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread ready 3
//01:48:08.736 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread continue 3
//01:48:08.736 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample1 - thread continue 2
设定阻塞时间一
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
* @author scottxuan
*/
@Slf4j
public class CyclicBarrierExample2 {
//线程数
private final static int threadNum = 4;
//初始化线程同步数量
final static CyclicBarrier barrier = new CyclicBarrier(2);
public static void main(String[] args) throws InterruptedException {
ExecutorService service = Executors.newCachedThreadPool();
for (int i = 0; i < threadNum; i++) {
final int num = i;
service.execute(()->{
update(num);
});
Thread.sleep(2000);
}
service.shutdown();
}
public static void update(int num){
try {
log.info("thread ready {}",num);
//线程阻塞
barrier.await(1000, TimeUnit.MILLISECONDS);
log.info("thread continue {}",num);
} catch (Exception e) {
log.error("barrier await error");
}
}
}
//输出结果 总共4个线程 同步数为2 每个线程阻塞了1秒后 解除阻塞 不符合同步的数量(同步数为2) 报错
//02:05:32.487 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 0
//02:05:33.497 [pool-1-thread-1] ERROR scottxuan.cyclicbarrier.CyclicBarrierExample2 - barrier await error
//02:05:34.492 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 1
//02:05:34.492 [pool-1-thread-1] ERROR scottxuan.cyclicbarrier.CyclicBarrierExample2 - barrier await error
//02:05:36.504 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 2
//02:05:36.504 [pool-1-thread-1] ERROR scottxuan.cyclicbarrier.CyclicBarrierExample2 - barrier await error
//02:05:38.516 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 3
//02:05:38.516 [pool-1-thread-1] ERROR scottxuan.cyclicbarrier.CyclicBarrierExample2 - barrier await error
设定阻塞时间二
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
/**
* @author scottxuan
*/
@Slf4j
public class CyclicBarrierExample2 {
//线程数
private final static int threadNum = 2;
//初始化线程同步数量
final static CyclicBarrier barrier = new CyclicBarrier(1);
public static void main(String[] args) throws InterruptedException {
ExecutorService service = Executors.newCachedThreadPool();
for (int i = 0; i < threadNum; i++) {
final int num = i;
service.execute(()->{
update(num);
});
Thread.sleep(2000);
}
service.shutdown();
}
public static void update(int num){
try {
log.info("thread ready {}",num);
//线程阻塞
barrier.await(1000, TimeUnit.MILLISECONDS);
log.info("thread continue {}",num);
} catch (Exception e) {
log.error("barrier await error");
}
}
}
//结果输出 总共2个线程 同步数为1 线程阻塞了1秒后 解除阻塞 符合同步的数量(同步数量为1) 直接执行await之后代码
//02:08:40.742 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 0
//02:08:40.746 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread continue 0
//02:08:42.751 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread ready 1
//02:08:42.752 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample2 - thread continue 1
带runable的构造方法
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.CyclicBarrier;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
/**
* @author scottxuan
*/
@Slf4j
public class CyclicBarrierExample3 {
//线程数
private final static int threadNum = 2;
//初始化线程同步数量
final static CyclicBarrier barrier = new CyclicBarrier(2,() -> {
log.info("is ready over");
});
public static void main(String[] args) throws InterruptedException {
ExecutorService service = Executors.newCachedThreadPool();
for (int i = 0; i < threadNum; i++) {
final int num = i;
service.execute(()->{
update(num);
});
}
service.shutdown();
}
public static void update(int num){
try {
log.info("thread ready {}",num);
//线程阻塞
barrier.await();
log.info("thread continue {}",num);
} catch (Exception e) {
e.printStackTrace();
}
}
}
//输出结果 ready 就绪之后, 构造方法中 runable方法执行 runable执行结束后 await()之后的代码开始执行
//02:13:09.648 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample3 - thread ready 1
//02:13:09.648 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample3 - thread ready 0
//02:13:09.652 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample3 - is ready over
//02:13:09.652 [pool-1-thread-1] INFO scottxuan.cyclicbarrier.CyclicBarrierExample3 - thread continue 0
//02:13:09.652 [pool-1-thread-2] INFO scottxuan.cyclicbarrier.CyclicBarrierExample3 - thread continue 1
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