线程

Day30.线程

ThreadPoolExecutor源码分析

一、Java构建线程方式

1. 继承thread类

   public class TestThread extends Thread {}
   

2. 实现Runnable

3. 实现Callable,可以返回值

4. 线程池方式(java 提供了构建线程池的方式)

   Executors
   

   规范中不允许使用下面的方式创建线程池，这种方式对线程控制力度比较低,推荐手动创建线程池.

   ExecutorService executorService = Executors.newFixedThreadPool(1);
   

二、线程池7个参数

• corePoolSize:线程数

• maximumPoolSize:最大线程数

• keepAliveTime:空闲时间

• unit:keepAliveTime参数的时间单位

• workQueue:阻塞队列

• threadFactory:线程工厂.可以给线程指定一个名称

• handler:拒绝策略

  Creates a new ThreadPoolExecutor with the given initial parameters.
  形参:
  corePoolSize – the number of threads to keep in the pool, even if they are idle, unless allowCoreThreadTimeOut is set
  maximumPoolSize – the maximum number of threads to allow in the pool
  keepAliveTime – when the number of threads is greater than the core, this is the maximum time that excess idle threads will wait for new tasks before terminating.
  unit – the time unit for the keepAliveTime argument
  workQueue – the queue to use for holding tasks before they are executed. This queue will hold only the Runnable tasks submitted by the execute method.
  threadFactory – the factory to use when the executor creates a new thread
  handler – the handler to use when execution is blocked because the thread bounds and queue capacities are reached
  抛出:
  IllegalArgumentException – if one of the following holds: corePoolSize < 0 keepAliveTime < 0 maximumPoolSize <= 0 maximumPoolSize < corePoolSize
  NullPointerException – if workQueue or threadFactory or handler is null
  
  public ThreadPoolExecutor(int corePoolSize,
                                int maximumPoolSize,
                                long keepAliveTime,
                                TimeUnit unit,
                                BlockingQueue<Runnable> workQueue,
                                ThreadFactory threadFactory,
                                RejectedExecutionHandler handler) {...}
  

三、线程池的执行流程

• 线程池执行流程