java 多线程通知 CountDownLatch 倒数计数器的使用
package com.hra.riskprice; import com.hra.riskprice.SysEnum.Factor_Type; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import java.text.SimpleDateFormat; import java.util.*; import java.util.concurrent.*; class R1 implements Runnable{ public static int i=1; @Override public void run() { try { SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); Date d = new Date(); String dateNowStr = sdf.format(d); System.out.println("before:"); System.out.println(dateNowStr); System.out.println("当前值是:"+i++); Thread.sleep(3000); System.out.println("after:"); System.out.println(dateNowStr); } catch (InterruptedException e) { e.printStackTrace(); } } } @SpringBootApplication public class RiskpriceApplication { public static long time (int concurrency, final Runnable action)throws InterruptedException{ final CountDownLatch ready=new CountDownLatch(concurrency); final CountDownLatch start=new CountDownLatch(1); final CountDownLatch done=new CountDownLatch(concurrency); for(int i=0;i<5;i++){ new Thread(new Runnable() { @Override public void run() { ready.countDown(); try { start.await(); action.run(); } catch (InterruptedException e) { Thread.currentThread().interrupt(); }catch (Exception ex){ String msg=ex.getMessage(); } finally { done.countDown(); } } }).start(); } ready.await(); long startNano=System.nanoTime(); start.countDown(); done.await(); return System.nanoTime()-startNano; } public static void main(String[] args) { R1 r=new R1(); try{ long l=time(5,r)/1000; System.out.println("用时:"+l); } catch (InterruptedException e){ Thread.currentThread().interrupt(); } } } 注意 for(int i=0;i<concurrency;i++)代码concurrency的当前值是5,这个数值如果小于5,就会造成线程饥饿死锁 ,也就是说至少要创建与指定并发级别一样多的线程,否则这个测试永远不会结束
还有一点,我上面没有使用线程池,如果知道执行的线程数目,那么可用如下的方法替代 使用 ExecutorService excutor= Executors.newFixedThreadPool(concurrency),如此更优
public static long time (int concurrency, final Runnable action)throws InterruptedException{
ExecutorService excutor= Executors.newFixedThreadPool(concurrency);
final CountDownLatch ready=new CountDownLatch(concurrency);
final CountDownLatch start=new CountDownLatch(1);
final CountDownLatch done=new CountDownLatch(concurrency);
for(int i=0;i<concurrency;i++){
excutor.execute(new Runnable() {
@Override
public void run() {
ready.countDown();
try {
start.await();
action.run();
} catch (InterruptedException e) {
Thread.currentThread().interrupt();
}catch (Exception ex){
String msg=ex.getMessage();
}
finally {
done.countDown();
}
}
});
}
ready.await();
long startNano=System.nanoTime();
start.countDown();
done.await();
return System.nanoTime()-startNano;
}