[JUC source code] thread pool: ThreadPoolExecutor (1) inheritance relationship analysis

Thread pool series:

• [JUC source code] thread pool: ThreadPoolExecutor (1) inheritance relationship analysis
• [JUC source code] Thread pool: ThreadPoolExecutor (two) underlying structure analysis
• [JUC source code] Thread pool: ThreadPoolExecutor (3) Worker design ideas and source code analysis
• [JUC source code] Thread pool: ThreadPoolExecutor (four) source code analysis of task execution process
• [JUC source code] thread pool: ThreadPoolExecutor (5) summary
• [JUC source code] Thread pool: Parameter setting ideas for creating thread pool &Excutors
• [JUC source code] Thread Pool: Several questions about ThreadPool

Before looking at the source code of ThreadPoolExecutor, let's take a look at the inheritance relationship of ThreadPoolExecutor

1.Executor

Define the execute method to execute the task, the input parameter is Runnable, no output parameter

public interface Executor {
    
    
    void execute(Runnable command);
}

2.ExecutorService

The function of Executor is too weak. ExecutorService enriches the functions of task execution and management. The main code is as follows:

public interface ExecutorService extends Executor {
    
    
    // 提交有返回值的任务，使用 get 方法可以阻塞等待任务的执行结果返回
    <T> Future<T> submit(Callable<T> task);
    // 提交没有返回值的任务，如果使用 get 方法的话，任务执行完之后得到的是 null 值
    Future<?> submit(Runnable task);
    
    // 给定任务集合，返回已经执行完成的 Future 集合，每个返回的 Future 都是 isDone = true 的状态
    <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks)
        throws InterruptedException;
    // 给定任务中有一个执行成功就返回，如果抛异常，其余未完成的任务将被取消
    <T> T invokeAny(Collection<? extends Callable<T>> tasks)
        throws InterruptedException, ExecutionException;
    
    // 关闭，不会接受新的任务，也不会等待未完成的任务
    // 如果需要等待未完成的任务，可以使用 awaitTermination 方法
    void shutdown();
    // 在超时时间内，等待剩余的任务终止
    boolean awaitTermination(long timeout, TimeUnit unit)
        throws InterruptedException;
    
    // executor 是否已经关闭了，返回值 true 表示已关闭
    boolean isShutdown();
    // 所有的任务是否都已经终止，是的话，返回 true
    boolean isTerminated();
    
}

3.AbstractExecutorService

• Abstract class, which encapsulates many general functions of Executor
• Implemented some ExecutorService methods

public abstract class AbstractExecutorService implements ExecutorService {
    
    
   
    // 将Callabbe，想要返回值的Runnable转化成Callable
    protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) {
    
    
        return new FutureTask<T>(runnable, value);
    }
    // FutureTask(Runnable,T) -> RunnableFuture -> Runnable
    protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) {
    
    
        return new FutureTask<T>(callable);
    }
    
    // submit调用的还是execute
    // 只不过将Callable，要返回值的Runnable提前转化成了RunnableFuture
    // 提交无返回值的任务
    public Future<?> submit(Runnable task) {
    
    
        if (task == null) throw new NullPointerException();
        // ftask 其实是 FutureTask
        RunnableFuture<Void> ftask = newTaskFor(task, null);
        execute(ftask);
        return ftask;
    }
    
    // 提交有返回值的任务
    public <T> Future<T> submit(Callable<T> task) {
    
    
        if (task == null) throw new NullPointerException();
        // ftask 其实是 FutureTask
        RunnableFuture<T> ftask = newTaskFor(task);
        execute(ftask);
        return ftask;
    }
}