package com.study.concurrent.demo;
import lombok.extern.slf4j.Slf4j;
import org.junit.jupiter.api.Test;
import org.springframework.util.StopWatch;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
@Slf4j
class SynchronizedTests {
@Test
public void doFor() throws InterruptedException {
StopWatch sw = new StopWatch();
CountDownLatch countDownLatch = new CountDownLatch(2);
sw.start("程序开始执行");
ExecutorService executorService = Executors.newCachedThreadPool();
executorService.execute(()->{
forValue();
countDownLatch.countDown();
});
executorService.execute(()->{
forValue();
countDownLatch.countDown();
});
countDownLatch.await();
executorService.shutdown();
sw.stop();
log.info("程序用时,{}",sw.prettyPrint());
}
public synchronized void forValue(){
for (int i = 0; i < 1000000; i++) {
log.info("输出,{}",i);
}
}
}
//运行时间
//1040582528 no synchronized
//942745806 synchronized
各位看官过来看看嘛,synchronized修改的forValue方法,两个线程会顺序执行,第一个线程先输出100万次,第二个线程才开始输入100万。如果forValue方法没被synchronized修饰两个线程是同时执行,顺序交替无序。按理没有synchronized的执行时间应该更短。但是实际测的时间两者相差无几,这是为啥。