多线程工具

1.semaphore
控制一个文件允许方法的并发数，即同时访问这个文件的线程数量。

public class TestThread {    public static void main(String[] args) {        //创建线程池        ExecutorService service=Executors.newCachedThreadPool();        //设置最大并发访问次数        final Semaphore sp=new Semaphore(3);        for(int i=0;i<10;i++){            Runnable runnable=new Runnable(){                public void run() {                    try {                        //获得一个允许                        sp.acquire();                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println("线程"+Thread.currentThread().getName()+                            "进入，当前已有"+(3-sp.availablePermits())+"线程");                    try {                        Thread.sleep(3000);                    } catch (InterruptedException e) {                        e.printStackTrace();                    }                    System.out.println("线程"+Thread.currentThread().getName()+"即将离开");                    sp.release();                }            };            //执行线程            service.execute(runnable);        }    }}

控制台执行结果

线程pool-1-thread-1进入，当前已有3线程线程pool-1-thread-3进入，当前已有3线程线程pool-1-thread-2进入，当前已有3线程线程pool-1-thread-3即将离开线程pool-1-thread-1即将离开线程pool-1-thread-2即将离开线程pool-1-thread-4进入，当前已有1线程线程pool-1-thread-5进入，当前已有2线程线程pool-1-thread-6进入，当前已有3线程线程pool-1-thread-5即将离开线程pool-1-thread-4即将离开线程pool-1-thread-6即将离开线程pool-1-thread-8进入，当前已有3线程线程pool-1-thread-7进入，当前已有3线程线程pool-1-thread-9进入，当前已有3线程线程pool-1-thread-8即将离开线程pool-1-thread-9即将离开线程pool-1-thread-7即将离开线程pool-1-thread-10进入，当前已有3线程线程pool-1-thread-10即将离开

2.CyclicBarrier
所有线程彼此等待，所有线程都执行完一段代码后，在各自执行下面的代码

public class TestThread2 {    public static void main(String[] args) {        //创建线程池        ExecutorService service=Executors.newCachedThreadPool();        //设置同时等待数量        final CyclicBarrier sp=new CyclicBarrier(3);        for(int i=0;i<3;i++){            Runnable runnable=new Runnable(){                public void run() {                    try {                    Thread.sleep((long)Math.random()*10000);                    System.out.println("线程"+Thread.currentThread().getName()+                            "进入集合地点1，当前已有"+(sp.getNumberWaiting()+1)+"线程等待,"+  (sp.getNumberWaiting()==3?"都到了，一起走":""));                        sp.await();                    Thread.sleep((long)Math.random()*10000);                    System.out.println("线程"+Thread.currentThread().getName()+                            "进入集合地点2，当前已有"+(sp.getNumberWaiting()+1)+"线程等待,"+(sp.getNumberWaiting()==3?"都到了，一起走":""));                        sp.await();                } catch (Exception e) {                    e.printStackTrace();                }            }            };            //执行线程            service.execute(runnable);    }    }}

执行结果

线程pool-1-thread-2进入集合地点1，当前已有1线程等待,线程pool-1-thread-1进入集合地点1，当前已有2线程等待,线程pool-1-thread-3进入集合地点1，当前已有3线程等待,都到了，一起走线程pool-1-thread-3进入集合地点2，当前已有1线程等待,线程pool-1-thread-2进入集合地点2，当前已有1线程等待,线程pool-1-thread-1进入集合地点2，当前已有3线程等待,都到了，一起走

3.CountDownLatch
倒计时计数器，CountDownLatch对象的countDown方法，将计数器减1，当计数器到达0时候，所有等待者开始执行开始执行。实现一个人等待多个人，或多个人等待一个人

public class CountdownLatchTest {    public static void main(String[] args) {        ExecutorService service = Executors.newCachedThreadPool();        final CountDownLatch cdOrder = new CountDownLatch(1);        final CountDownLatch cdAnswer = new CountDownLatch(3);              for(int i=0;i<3;i++){            Runnable runnable = new Runnable(){                    public void run(){                    try {                        System.out.println("线程" + Thread.currentThread().getName() +                                 "正准备接受命令");                                             cdOrder.await();                        System.out.println("线程" + Thread.currentThread().getName() +                         "已经接受命令");                                                      Thread.sleep((long)(Math.random()*10000));                          System.out.println("线程" + Thread.currentThread().getName() +                                 "等待处理结果");                                              cdAnswer.countDown();                                           } catch (Exception e) {                        e.printStackTrace();                    }                               }            };            service.execute(runnable);        }               try {            Thread.sleep((long)(Math.random()*10000));            System.out.println("线程" + Thread.currentThread().getName() +                     "即将发送命令");                                  cdOrder.countDown();            System.out.println("线程" + Thread.currentThread().getName() +             "线程已经发送命令");                cdAnswer.await();            System.out.println("线程" + Thread.currentThread().getName() +             "已收到响应结果");         } catch (Exception e) {            e.printStackTrace();        }                       service.shutdown();    }}

执行结果

线程pool-1-thread-1正准备接受命令线程pool-1-thread-3正准备接受命令线程pool-1-thread-2正准备接受命令线程main即将发送命令线程main线程已经发送命令线程pool-1-thread-2已经接受命令线程pool-1-thread-1已经接受命令线程pool-1-thread-3已经接受命令线程pool-1-thread-1等待处理结果线程pool-1-thread-3等待处理结果线程pool-1-thread-2等待处理结果线程main已收到响应结果

4.Exchange
用于两个线程之间数据交换，一个线程拿出数据要一直等待直到另外一个线程拿出数据，才能交换

public class ExchangerTest {    public static void main(String[] args) {        ExecutorService service = Executors.newCachedThreadPool();        final Exchanger exchanger = new Exchanger();        service.execute(new Runnable(){            public void run() {                try {                               String data1 = "黄金";                    System.out.println("线程" + Thread.currentThread().getName() +                     "正准备把" + data1 +"换出");                    Thread.sleep((long)(Math.random()*10000));                    String data2 = (String)exchanger.exchange(data1);                    System.out.println("线程" + Thread.currentThread().getName() +                     "换成的数据为" + data2);                }catch(Exception e){                        }            }           });        service.execute(new Runnable(){            public void run() {                try {                                   String data1 = "钻石 ";                    System.out.println("线程" + Thread.currentThread().getName() +                     "正准备把" + data1 +"换出");                    Thread.sleep((long)(Math.random()*10000));                                      String data2 = (String)exchanger.exchange(data1);                    System.out.println("线程" + Thread.currentThread().getName() +                     "换成的数据为" + data2);                }catch(Exception e){                }                           }           });         }}

执行结果

线程pool-1-thread-1正准备把zxx换出线程pool-1-thread-2正准备把lhm换出线程pool-1-thread-2换成的数据为zxx线程pool-1-thread-1换成的数据为lhm