[笔记]Executors框架

框架结构

任务：Runnable和Callable

任务的执行：Executor接口->ExecutorService接口

ThreadPoolExecutor

ScheduledThreadPoolExecutor

异步计算的结果：Future接口->FutureTask类

ThreadPoolExecutor

new ThreadPoolExecutor(corePoolSize,maximumPoolSize,keepAliveTime,timeunit,runnableTaskQueue,handler)

corePoolSize: 预热到这个线程大小，不再创建新线程，就要放到runnableTaskQueue里面

maximumPoolSize：只有runnableTaskQueue满了，才会创建新线程，最大线程数不超过这个值

runnableTaskQueue： 任务队列

handler：饱和策略

AbortPolicy：直接抛弃

通常使用工厂类Executors创建：

1.FixedThreadPool：满足资源管理的需求，适合负载比较重的服务器

public staticExecutorService newFixedThreadPool(int nThreads)
public staticExecutorService newFixedThreadPool(int nThreads,ThreadFactory threadFactory)

源代码：

public static

2.SingleThreadPool: 满足保证顺序的执行每个任务，并且在任意时间点，不会有多个线程是活动的场景

public staticExecutorService newSingleThreadPool()
public staticExecutorService newSingleThreadPool(ThreadFactory threadFactory)

3.CachedThreadPool:大小无界，适用于很多短期异步的小程序，或者是负载较轻的服务器

public staticExecutorService newCachedThreadPool()
public staticExecutorService newCachedThreadPool(ThreadFactory threadFactory)

ScheduledThreadPoolExecutor

使用工厂类Executors创建

1.ScheduledThreadPoolExecutor:

public staticExecutorService newScheduledThreadPool(int nThreads)
public staticExecutorService newScheduledThreadPool(int nThreads,ThreadFactory threadFactory)

2.SingleThreadScheduledExecutor:

public staticExecutorService newSingleThreadScheduledExecutor()
public staticExecutorService newSingleThreadScheduledExecutor(ThreadFactory threadFactory)

Future接口

当我们把Runnable接口或者Callable接口submit给ThreadPoolExecutor时，会返回一个FutureTask对象，API：

<T> Future<T> submit(Callable<T> Task)
<T> Future<T> submit(Runnable Task,T result)
Future<?> submit(Runnable Task)

Runnable和Callable接口

Executors提供的：

public staticCallable<Object> callable(Runnable task)
public static<T>Callable<T> callable(Runnable task,T Result)