Java多线程与并发库
同步方式
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import javax.xml.stream.events.StartDocument; public class TestSynchronized { public static void main(String[] args) { // TODO Auto-generated method stub TestSynchronized test = new TestSynchronized(); test.init(); } void init() { final Outputer outputer = new Outputer(); new Thread(new Runnable(){ @Override public void run() { // TODO Auto-generated method stub while(true){ try { Thread.sleep(10); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } outputer.Output("wangyuyuyuyuyuyuyuyu"); } } }){ }.start(); new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub while(true){ try { Thread.sleep(10); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } outputer.Output("zhouzhanzhaozhaozhaozhao"); } } }){ }.start(); } class Outputer{ final static String lockKey = "lock"; //定义输出函数 //第一种方式,提供某个锁 public void Output(String name){ int len = name.length(); synchronized (lockKey) { for (int i = 0; i < len; i++){ System.out.print(name.charAt(i)); } System.out.println(); } } //第二种方式,锁住自己 public void Output1(String name){ int len = name.length(); synchronized (this) { //也可以用Outputer.class for (int i = 0; i < len; i++){ System.out.print(name.charAt(i)); } System.out.println(); } } //第三种方式,函数前面加关键字synchronized public synchronized void Output2(String name){ int len = name.length(); for (int i = 0; i < len; i++){ System.out.print(name.charAt(i)); } System.out.println(); } } }
定时器Timer
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import java.util.Timer; import java.util.TimerTask; public class TimerTest { public static void main(String[] args){ new Timer().schedule(new TimerTask(){ @Override public void run() { // TODO Auto-generated method stub System.out.println("boom"); } }, 3000); } }
HashMap存储线程
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import java.util.HashMap; import java.util.Map; import java.util.Random; public class TestThreadMap { private static HashMap<Thread, Integer> map = new HashMap<Thread, Integer>(); public static void main(String[] args) { //TestThreadMap testThreadMap = new TestThreadMap(); for (int i = 0; i < 2; i++) { new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub int data = new Random().nextInt(); map.put(Thread.currentThread(), data); new A().Get(); new B().Get(); } }){}.start(); } } static class A{ public void Get(){ int data = map.get(Thread.currentThread()); System.out.println("A from " + Thread.currentThread().getName() + " get data " + data); } } static class B{ public void Get(){ int data = map.get(Thread.currentThread()); System.out.println("B from " + Thread.currentThread().getName() + " get data " + data); } } }
ThreadLocal类似HashMap存储线程
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import java.util.HashMap; import java.util.Map; import java.util.Random; public class TestThreadMap { private static HashMap<Thread, Integer> map = new HashMap<Thread, Integer>(); public static void main(String[] args) { //TestThreadMap testThreadMap = new TestThreadMap(); for (int i = 0; i < 2; i++) { new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub int data = new Random().nextInt(); map.put(Thread.currentThread(), data); new A().Get(); new B().Get(); } }){}.start(); } } static class A{ public void Get(){ int data = map.get(Thread.currentThread()); System.out.println("A from " + Thread.currentThread().getName() + " get data " + data); } } static class B{ public void Get(){ int data = map.get(Thread.currentThread()); System.out.println("B from " + Thread.currentThread().getName() + " get data " + data); } } }
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import java.util.Random; public class TestThreadlocal_2 { public static void main(String[] args) { // TODO Auto-generated method stub for (int i = 0; i < 2; i++){ new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub int data = new Random().nextInt(); MyData.getInstance().setName("myData" + data); MyData.getInstance().setAge(data); new A().Get(); new B().Get(); } }){}.start(); } } static class A{ public void Get(){ MyData data = MyData.getInstance(); System.out.println("A from " + Thread.currentThread().getName() + " get data " + data.getName() + ", " + data.getAge()); } } static class B{ public void Get(){ MyData data = MyData.getInstance(); System.out.println("B from " + Thread.currentThread().getName() + " get data " + data.getName() + ", " + data.getAge()); } } } class MyData{ String name; int age; public static /*synchronized*/ MyData getInstance(){ MyData instance = threadLocal.get(); if (instance == null){ //不存在就创建一个与本线程有关的实例对象 instance = new MyData(); threadLocal.set(instance); } return instance; } //private static MyData instance = null; private static ThreadLocal<MyData> threadLocal = new ThreadLocal<MyData>(); public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } }
线程池
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import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; public class TestThreadPool { public static void main(String[] args){ //固定大小的线程池 ExecutorService threadPool = Executors.newFixedThreadPool(3); //缓存线程池,当线程不够用时会自动增加,多了会自动减少 //ExecutorService threadPool = Executors.newCachedThreadPool(); //单一线程池,线程死了可以重新启动 //ExecutorService threadPool = Executors.newSingleThreadExecutor(); for (int i = 1; i <= 10; i++){ final int taskid = i; threadPool.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub for (int j = 1; j <= 10; j++) { System.out.println(Thread.currentThread().getName() + " is loop of " + j + " for task of " + taskid); } } }); } System.out.println("all have finished"); threadPool.shutdown(); //线程池里没有任务了,线程池才关闭,等10个任务都完成后才关闭 //threadPool.shutdownNow(); //一个线程完成之后立马关闭,此时只完成了3个任务 /*//定时器线程池 Executors.newScheduledThreadPool(3).schedule( new Runnable() { @Override public void run() { // TODO Auto-generated method stub System.out.println("booming"); } }, 6, TimeUnit.SECONDS); //多长时间后执行任务 */ Executors.newScheduledThreadPool(3).scheduleAtFixedRate( //以固定频率执行任务 new Runnable() { @Override public void run() { // TODO Auto-generated method stub System.out.println("booming"); } }, 6, //初始时间 2, //间隔时间 TimeUnit.SECONDS); } }
锁Lock
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import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock; import javax.xml.stream.events.StartDocument; public class TestLock { public static void main(String[] args) { // TODO Auto-generated method stub TestLock test = new TestLock(); test.init(); } void init() { final Outputer outputer = new Outputer(); new Thread(new Runnable(){ @Override public void run() { // TODO Auto-generated method stub while(true){ try { Thread.sleep(10); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } outputer.Output("wangyuyuyuyuyuyuyuyu"); } } }){ }.start(); new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub while(true){ try { Thread.sleep(10); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } outputer.Output("zhouzhanzhaozhaozhaozhao"); } } }){ }.start(); } class Outputer{ Lock lock = new ReentrantLock(); //锁 public void Output(String name){ int len = name.length(); lock.lock(); try { for (int i = 0; i < len; i++){ System.out.print(name.charAt(i)); } System.out.println(""); } finally{ // TODO: handle exception lock.unlock(); } } } }
读写锁ReadWriterLock
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import java.util.HashMap; import java.util.concurrent.locks.ReadWriteLock; import java.util.concurrent.locks.ReentrantReadWriteLock; public class TestReadWriterLock { HashMap<String, Object> mp = new HashMap<String, Object>(); private ReadWriteLock rwl = new ReentrantReadWriteLock(); public Object Get(String key){ rwl.readLock().lock(); Object value = null; try { value = mp.get(key); if (value == null) { rwl.readLock().unlock(); rwl.writeLock().lock(); try { if (value == null){ value = "aaa"; } } finally { // TODO: handle finally clause rwl.writeLock().unlock(); } rwl.readLock().lock(); } } finally { rwl.readLock().unlock(); } return value; } }
信号灯Semaphere(控制当前运行的线程个数)
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import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Semaphore; import java.util.function.IntToDoubleFunction; public class TestSemaphere { public static void main(String[] args) { // TODO Auto-generated method stub /*1.创建线程池 *2.创建信号灯,大小为3 *3.循环10次,Runnable里设置信号灯acqure */ ExecutorService es = Executors.newCachedThreadPool(); Semaphore semaphore = new Semaphore(3); for(int i = 0; i < 10; i++){ es.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { semaphore.acquire(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } System.out.println("线程" + Thread.currentThread().getName() + "进入"); try { Thread.sleep((int)Math.random() * 10000); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } System.out.println("线程" + Thread.currentThread().getName() + "即将结束"); semaphore.release(); System.out.println("线程" + Thread.currentThread().getName() + "已结束"); es.shutdown(); } }); } } }
数据交换Exchanger(当两个数据都到达后才能进行交换,否则阻塞)
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import java.util.concurrent.Exchanger; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestExchanger { public static void main(String[] args) { // TODO Auto-generated method stub ExecutorService es = Executors.newCachedThreadPool(); Exchanger<String> exchanger = new Exchanger<String>(); es.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { String data1 = "x"; System.out.println("线程" + Thread.currentThread().getName() + "正在把数据" + data1 + "发送出去"); Thread.sleep((int)(Math.random() * 5000)); String getData = exchanger.exchange(data1); System.out.println("线程" + Thread.currentThread().getName() + "接受到的数据为: " + getData); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } }); es.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { String data1 = "y"; System.out.println("线程" + Thread.currentThread().getName() + "正在把数据" + data1 + "发送出去"); Thread.sleep((int)(Math.random() * 5000)); String getData = exchanger.exchange(data1); System.out.println("线程" + Thread.currentThread().getName() + "接受到的数据为: " + getData); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } }); } }
同步屏障CyclicBarrier(多个线程彼此等待,集合后再往后运行)
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import java.util.concurrent.CyclicBarrier; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestCyclicBarrier { //多个线程彼此等待,集合后再运行 public static void main(String[] args) { // TODO Auto-generated method stub //创建线程池和CyclicBarrier,同时运行多个线程,调用await ExecutorService es = Executors.newCachedThreadPool(); final CyclicBarrier cb = new CyclicBarrier(3); for (int i = 0; i < 3; i++){ es.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { Thread.sleep((int)(Math.random() * 1000)); System.out.println("线程" + Thread.currentThread().getName() + "到达集合点1"); System.out.println("当前有" + (cb.getNumberWaiting()+1) + "人在等待"); cb.await(); Thread.sleep((int)(Math.random() * 1000)); System.out.println("线程" + Thread.currentThread().getName() + "到达集合点2"); System.out.println("当前有" + (cb.getNumberWaiting()+1) + "人在等待"); cb.await(); Thread.sleep((int)(Math.random() * 1000)); System.out.println("线程" + Thread.currentThread().getName() + "到达集合点3"); System.out.println("当前有" + (cb.getNumberWaiting()+1) + "人在等待"); cb.await(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } }); } es.shutdown(); } }
CountDownLatch(类似倒计时计数器,当计数减为0时,所有等待者才开始执行)
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import java.util.concurrent.CountDownLatch; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class TestCountDownLatch { //类似倒计时计数器,当计数减为0的时候,所有等待者才开始执行 public static void main(String[] args) { // TODO Auto-generated method stub //创建两个计数器,一个为1,一个为3,代表一个裁判员,三个运动员,裁判员在未下达命令前运动员等待,下达命令后才执行 //等三个运动员都到达终点后,裁判员才公布成绩 ExecutorService es = Executors.newCachedThreadPool(); CountDownLatch cdOrder = new CountDownLatch(1); CountDownLatch cdAnswer = new CountDownLatch(3); for (int i = 0; i < 3; i++) { final int id = i; es.execute(new Runnable() { @Override public void run() { // TODO Auto-generated method stub try { System.out.println("运动员" + id + "正准备接受命令"); cdOrder.await(); System.out.println("运动员"+ id + "接受到命令"); Thread.sleep((int)(Math.random() * 5000)); System.out.println("运动员" + id + "到达终点"); cdAnswer.countDown(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } }); } try { Thread.sleep(1000); System.out.println("裁判员发出指令"); cdOrder.countDown(); System.out.println("裁判员等待所有运动员到达终点"); cdAnswer.await(); System.out.println("裁判员公布成绩"); } catch (Exception e) { // TODO: handle exception } } }
Callable和Future
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import java.util.Random; import java.util.concurrent.Callable; import java.util.concurrent.CompletionService; import java.util.concurrent.ExecutionException; import java.util.concurrent.ExecutorCompletionService; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; import java.util.concurrent.TimeoutException; public class TestCallableAndFuture { public static void main(String[] args) throws InterruptedException, ExecutionException, TimeoutException{ ExecutorService threadPool = Executors.newSingleThreadExecutor(); Future future = threadPool.submit(new Callable<String>() { @Override public String call() throws Exception { // TODO Auto-generated method stub Thread.sleep(2000); return "hello"; } }); System.out.println("得到结果: " + future.get()); //callable完成任务返回结果,由future去拿,需要等待一段时间 //System.out.println("得到结果: " + future.get(1, TimeUnit.SECONDS)); //要在规定的时间内得到结果,如果得不到就抛出异常 //CompletionService 用于提交一组callable任务,并用take方法得到一个已完成任务的future对象 ExecutorService threadPool2 = Executors.newFixedThreadPool(10); CompletionService<Integer> completionService = new ExecutorCompletionService<Integer>(threadPool2); for (int i = 1; i <= 10; i++){ final int taskid = i; completionService.submit(new Callable<Integer>() { @Override public Integer call() throws Exception { // TODO Auto-generated method stub try { Thread.sleep(new Random().nextInt(5000)); } catch (Exception e) { // TODO: handle exception } return taskid; } }); } for (int i = 1; i <= 10; i++){ System.out.println(completionService.take().get()); } } }
阻塞队列ArrayBlockingQueue
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import java.util.concurrent.ArrayBlockingQueue; public class TestArrayBlockingQueue { //阻塞队列当队列为空时take会阻塞,当队列满时put会阻塞 //用两个阻塞队列模拟两个线程交替运行 //两个阻塞队列大小均设置为1,其中一个放一个数据 public static void main(String[] args) { // TODO Auto-generated method stub Business business = new Business(); new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub for (int j = 1; j <= 10; j++) { business.Sub(j); } } }){}.start(); for (int j = 1; j <= 10; j++) { business.Main(j); } } static class Business{ ArrayBlockingQueue abq1 = new ArrayBlockingQueue(1); ArrayBlockingQueue abq2 = new ArrayBlockingQueue(1); public Business() { try { abq2.put(1); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } public void Sub(int j){ try { abq1.put(1); for (int i = 1; i <= 10; i++){ System.out.println("sub thread " + i + " of loop " + j); } abq2.take(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } public void Main(int j){ try { abq2.put(1); for (int i = 1; i <= 10; i++){ System.out.println("main thread " + i + " of loop " + j); } abq1.take(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } } }
练习: 子线程运行10次,主线程运行20次,交替运行
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public class prictice_1 { //子线程运行10次,主线程运行20次 public static void main(String[] args) { // TODO Auto-generated method stub Business business = new Business(); new Thread(new Runnable() { @Override public void run() { // TODO Auto-generated method stub for (int j = 1; j <= 10; j++) { business.Sub(j); } } }){}.start(); for (int j = 1; j <= 10; j++) { business.Main(j); } } } class Business{ private boolean isSub = true; public synchronized void Sub(int j){ while (!isSub) { try { this.wait(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } for (int i = 1; i <= 10; i++){ System.out.println("sub thread " + i + " of loop " + j); } isSub = false; this.notify(); } public synchronized void Main(int j){ while (isSub){ try { this.wait(); } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } } for (int i = 1; i <= 20; i++){ System.out.println("main thread " + i + " of loop " + j); } isSub = true; this.notify(); } }