java线程池的使用

java自带的线程池

• 可缓存线程池

  特点：对线程的个数没有限制，无法控制线程的最大并发数
  使用：

  ExecutorService executorService = Executors.newCachedThreadPool()
  executorService .execute(Runnable MyRunnable)
  

• 定长线程池

  特点：指定最大线程的个数
  使用：

  ExecutorService executorService = Executors.newFixedThreadPool(10)
  executorService .execute(Runnable MyRunnable)
  

• 单线程线程池

  特点：先来的先执行，有顺序
  使用：

  ExecutorService executorService = Executors.newSingleThreadExecutor()
  executorService .execute(Runnable MyRunnable)
  

• 计划任务线程池

  特点：可以做定时任务
  使用：

  ExecutorService executorService = Executors.newScheduledThreadPool(10)
  schedule(Runnable MyRunnable,	//自定义Runnable
           long delay,	//时间数值，例：5
           TimeUnit unit)	//时间单位，例：TimeUnit.SECONDS(秒)
  

自定义线程池

ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(
											int corePoolSize,	//核心线程数，初始化线程数量
                              				int maximumPoolSize,	//最大线程数量
                             				long keepAliveTime,	//线程等待任务的最大空闲时间
                              				TimeUnit unit,		//时间单位
                              				BlockingQueue<Runnable> workQueue,//阻塞队列，存放还没有执行的线程任务
											ThreadFactory threadFactory,	//创建线程工厂，默认工厂：Executors.defaultThreadFactory()
                              				RejectedExecutionHandler handler//拒绝策略(丢弃任务抛异常，丢弃任务不抛异常，丢弃队列最前面的任务，有点用线程处理盖该任务)，默认：defaultHandler
                              				)

例：

ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(5,
        10,
        60,
        TimeUnit.SECONDS,
        new LinkedBlockingQueue<>(50),
        Executors.defaultThreadFactory(),
        new ThreadPoolExecutor.AbortPolicy());

threadPoolExecutor.execute(new Runnable() {
    @Override
    public void run() {
        System.out.println("我是 Runnable. ");
    }
});
Future<String> future = threadPoolExecutor.submit(new Callable<String>() {
    @Override
    public String call() throws Exception {
        System.out.println("我是 Callable. ");
        return "Callable";
    }
});
Object str = future.get();
//Object str = future.get(10,//最大等待时间
//          TimeUnit.SECONDS);//时间单位
System.out.println(str);