Thread - Thread Execution

线程运行工具也有两种方法实现：

1、Thread

2、ThreadPool

      - Executors.xxx.submit: 运行器  (submit, return Future)

      - ThreadPoolExecutor.execute: 线程池运行器  (execute, void)

主要区别：线程池循环使用线程池中的线程，减少创建和销毁线程。

可以用Future接收运行结果

运行体主要有两种方法实现：

1、Runnable(), run()

2、Callable(), call()

主要区别：Run 没有返回值，Call有返回值。

可以把运行体封装成FutureTask。

一、准备线程

1、Thread

Thread t = new Thread([Runnable | Callable]);

2、Thread Pool Executor

ExecutorService executor = Executors.newFixedThreadPool(n);  // n threads; newSingleThreadExecutor(), newScheduledThreadPool(), ...

二、运行体

1、Run

new Runnable() {  public void run() {...}}

2、Call

new Callable<String>() {  public String call() throws Exception {...; return ...}  // e.g. return String type}

3、FutureTask

Callable<String> task = ...;  // or RunnableFutureTask<String> ft = new FutureTask<String>(task);  // e.g.String

三、运行

1、Thread

t.start();

2、Thread Pool Executor

executor.submit([Callable | Runnable])

3、Future

Future<String> future = executor.submit(...)  // similar to thread.start

四、Sample

public class Thread01_future extends Thread {public static void main(String[] args) {// Future: 异步计算结果// Thread.start: 运行器// Executors.xxx.submit: 运行器// ThreadPoolExecutor.execute: 线程池运行器// (execute, void) (submit, return Future)// FutureTask: 异步计算任务// Runnable(), run(): 运行任务（运行类、运行方法，void）// Callable(), call(): 运行任务（运行类、运行方法，return）// test01();// test02();test03();}// Future: 异步计算结果// Executors.xxx.submit: 运行器// Runnable(), run(): 运行任务（运行类、运行方法，void）// Callable(), call(): 运行任务（运行类、运行方法，return）public static void test01() {// 创建一个执行任务的服务ExecutorService executor = Executors.newFixedThreadPool(3);try {// 1. A Runnable, however, does not return a result and cannot throw// checked exception.System.out.println("~~~1");Future<?> runnable1 = executor.submit(new Runnable() {@Overridepublic void run() {System.out.println("runnable1 running.");}});System.out.println("Runnable1:" + runnable1.get());// 2. CallableSystem.out.println("~~~2");Future<String> future1 = executor.submit(new Callable<String>() {@Overridepublic String call() throws Exception {return "result=task1";}});System.out.println("task1: " + future1.get());// 3. 对Callable调用cancel可以对对该任务进行中断System.out.println("~~~3");Future<String> future2 = executor.submit(new Callable<String>() {@Overridepublic String call() throws Exception {try {while (true) {System.out.println("task2 running.");Thread.sleep(50);}} catch (InterruptedException e) {System.out.println("Interrupted task2.");}return "task2=false";}});// 等待5秒后，再停止第二个任务。因为第二个任务进行的是无限循环Thread.sleep(101);System.out.println("task2 cancel: " + future2.cancel(true));// 4.用Callable时抛出异常则Future什么也取不到了// 获取第三个任务的输出，因为执行第三个任务会引起异常// 所以下面的语句将引起异常的抛出System.out.println("~~~4");Future<String> future3 = executor.submit(new Callable<String>() {@Overridepublic String call() throws Exception {throw new Exception("task3 throw exception!");}});// Thread.sleep(133);System.out.println("task3: " + future3.get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}// 停止任务执行服务executor.shutdownNow();}// FutureTask: 异步计算任务// Thread, Executors.xxx.submit: 运行器public static void test02() {Callable<String> task = new Callable<String>() {@Overridepublic String call() {System.out.println("Sleep start.");try {Thread.sleep(1000 * 3);} catch (InterruptedException e) {// TODO Auto-generated catch blocke.printStackTrace();}System.out.println("Sleep end.");return "time=" + System.currentTimeMillis();}};// 直接使用Thread的方式执行FutureTask<String> ft = new FutureTask<String>(task);Thread t = new Thread(ft);t.start();try {System.out.println("waiting execute result");System.out.println("result = " + ft.get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}// 使用Executors来执行System.out.println("=========");FutureTask<String> ft2 = new FutureTask<String>(task);Executors.newSingleThreadExecutor().submit(ft2);try {System.out.println("waiting execute result");System.out.println("result = " + ft2.get());} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();}}// ThreadPoolExecutor.execute: 线程池运行器public static void test03() {int produceTaskMaxNumber = 4;// 构造一个线程池ThreadPoolExecutor threadPool = new ThreadPoolExecutor(2, 4, 3,TimeUnit.SECONDS, new ArrayBlockingQueue<Runnable>(10),new ThreadPoolExecutor.DiscardOldestPolicy());ArrayList<FutureTask<String>> tasks = new ArrayList<FutureTask<String>>();for (int i = 1; i <= produceTaskMaxNumber; i++) {try {// 产生一个任务，并将其加入到线程池Callable<String> task = new Callable<String>() {@Overridepublic String call() {String task = "task@ ";System.out.println("put " + task);return task;}};FutureTask<String> futureTask = new FutureTask<String>(task);threadPool.execute(futureTask);tasks.add(futureTask);} catch (Exception e) {e.printStackTrace();}}for (FutureTask<String> futureTask : tasks) {// 1秒内获得结果 (1st arg: the maximum time to wait, 2nd arg: the time// unit of the timeout argument)String str = null;try {str = "stop " + futureTask.get(1, TimeUnit.SECONDS);} catch (InterruptedException e) {e.printStackTrace();} catch (ExecutionException e) {e.printStackTrace();} catch (TimeoutException e) {e.printStackTrace();}System.out.println(str);}}}