ExecutorService 介绍

1\. ThreadPoolExecutor
2\. ScheduledThreadPoolExecutor

ExecutorService的创建

newCachedThreadPool 创建一个可缓存的线程池,如果线程池长度超过处理需要,可灵活回收空闲线程,如果没有可以回收的,则新建线程。
newFixedThreadPool 创建一个定长的线程池,可控制线程最大并发数,超出的线程会在队列中等待。
newScheduledThreadPool 创建一个定长线程池,可以定时周期性执行任务。
newSingleThreadPool 创建一个单线程线程池,它只会用唯一的线程来执行任务,保证所有任务按照指定顺序来执行(FIFO,LIFO)

ExecutorService的使用

ExecutorService executorService = Executors.newFixedThreadPool(10);

executorService.execute(new Runnable() {
public void run() {
    System.out.println("入门小站");
}
});

executorService.shutdown();

ExecutorService的执行方法

execute(Runnable)
submit(Runnable)
submit(Callable)
invokeAny(...)
invokeAll(...)

execute(Runnable) 无法获取执行结果

ExecutorService executorService = Executors.newSingleThreadExecutor();

executorService.execute(new Runnable() {
public void run() {
    System.out.println("Asynchronous task");
}
});

executorService.shutdown();

submit(Runnable) 可以判断任务是否完成

Future future = executorService.submit(new Runnable() {
public void run() {
    System.out.println("Asynchronous task");
}
});

future.get();  //returns null if the task has finished correctly.

submit(Callable)可以获取返回结果

Future future = executorService.submit(new Callable(){
public Object call() throws Exception {
    System.out.println("Asynchronous Callable");
    return "Callable Result";
}
});

System.out.println("future.get() = " + future.get());

invokeAny(...)

ExecutorService executorService = Executors.newSingleThreadExecutor();

Set<Callable<String>> callables = new HashSet<Callable<String>>();

callables.add(new Callable<String>() {
public String call() throws Exception {
    return "Task 1";
}
});
callables.add(new Callable<String>() {
public String call() throws Exception {
    return "Task 2";
}
});
callables.add(new Callable<String>() {
    public String call() throws Exception {
    return "Task 3";
}
});

String result = executorService.invokeAny(callables);
System.out.println("result = " + result);
executorService.shutdown();

invokeAll(...)

ExecutorService executorService = Executors.newSingleThreadExecutor();

Set<Callable<String>> callables = new HashSet<Callable<String>>();

callables.add(new Callable<String>() {
public String call() throws Exception {
    return "Task 1";
}
});
callables.add(new Callable<String>() {
    public String call() throws Exception {
    return "Task 2";
}
});
callables.add(new Callable<String>() {
    public String call() throws Exception {
      return "Task 3";
   }
});

List<Future<String>> futures = executorService.invokeAll(callables);

for(Future<String> future : futures){
    System.out.println("future.get = " + future.get());
}

executorService.shutdown();