缺少更多功能,如更多执行,定期执行,线程中断
线程池中的状态:
import java.util.Date; import java.util.Timer; import java.util.TimerTask; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; @Slf4j public class ThreadPoolExample { public static void main(String[] args) { // ExecutorService executorService= Executors.newCachedThreadPool(); // ExecutorService executorService=Executors.newSingleThreadExecutor(); //ExecutorService executorService=Executors.newFixedThreadPool(3); ExecutorService executorService=Executors.newScheduledThreadPool(3); executorService.schedule(new Runnable(){ @Override public void run(){ log.warn("schedule run"); } },3, TimeUnit.SECONDS); //延迟一秒每隔一秒执行 executorService.scheduleAtFixedRate(new Runnable(){ @Override public void run(){ log.warn("schedule run"); } },1,3,TimeUnit.SECONDS); Timer timer=new Timer(); timer.schedule(new TimerTask() { @Override public void run() { log.warn("schedule run"); } },new Date(),5*1000); // for(int i=0;i<10;i++){ // final int index=i; // executorService.execute(new Runnable() { // @Override // public void run() { // log.info("task:{}",index); // } // }); // } executorService.shutdown(); } }
死锁案例:
import lombok.extern.slf4j.Slf4j; @Slf4j public class DeadLock implements Runnable { public int flag=1; private static Object o1=new Object(),o2=new Object(); @Override public void run(){ log.info("flag:",flag); if(flag==1){ synchronized (o1){ try { Thread.sleep(500); }catch (Exception e){ e.printStackTrace(); } synchronized (o2){ log.info("1"); } } } if(flag==0){ synchronized (o2){ try { Thread.sleep(500); }catch (Exception e){ e.printStackTrace(); } synchronized (o1){ log.info("0"); } } } } public static void main(String[] args) { DeadLock td1=new DeadLock(); DeadLock td2=new DeadLock(); td1.flag=1; td2.flag=0; new Thread(td1).start(); new Thread(td2).start(); } }
多线程并发的实践:
1.使用本地变量
2.使用不可变类
3.最小化锁的作用域范围
4.使用线程池的Executor,而不是直接new Thread执行
5.宁可使用同步,也不使用线程的wait和notify
6.使用BlockingQueue实现生产消费模式
7.使用并发集合不是加了锁的同步集合
8.使用Semaphore创建有界的访问
9.宁可使用同步代码块,也不使用同步的方法
10避免使用静态变量