11-案例实现

案例实现

按照如下步骤来实现本案例。

1．创建 Task 类，该类实现了 Runnable 接口：

public class Task implements Runnable {

2．在类中添加 long 型的私有属性 milliseconds ：

private final long milliseconds;

3．实现该类的构造函数以初始化其属性：

public Task (long milliseconds) {
  this.milliseconds=milliseconds;
}

4．实现接口中的 run() 方法，使线程休眠由 milliseconds 属性指定的毫秒数：

@Override
public void run() {
  System.out.printf("%s: Begin\n",
                    Thread.currentThread().getName());
  try {
    TimeUnit.MILLISECONDS.sleep(milliseconds);
  } catch (InterruptedException e) {
    e.printStackTrace();
  }
  System.out.printf("%s: End\n",
                    Thread.currentThread().getName());
}

5．实现本案例的主类，新建 Main 类和 main() 方法：

public class Main {
  public static void main(String[] args) throws Exception {

6．通过 Executors 类中的 newCachedThreadPool() 方法创建一个新的 Executor 对象：

ThreadPoolExecutor executor = (ThreadPoolExecutor)
                        Executors.newCachedThreadPool();

7．依次递交10个 Task 对象到执行器中，用一个随机数初始化这些对象：

Random random=new Random();
for (int i=0; i<10; i++) {
  Task task=new Task(random.nextInt(10000));
  executor.submit(task);
}

8．调用 showLog() 方法获得与执行器相关的信息，并休眠1s。以上步骤循环5次：

for (int i=0; i<5; i++){
  showLog(executor);
  TimeUnit.SECONDS.sleep(1);
}

9．用 shutdown() 方法关闭执行器：

  executor.shutdown();

10．继续通过 showLog() 方法获知与执行器相关的信息并休眠1s。以上步骤循环5次：

for (int i=0; i<5; i++){
  showLog(executor);
  TimeUnit.SECONDS.sleep(1);
}

11．通过 awaitTermination() 方法等待执行器执行结束：

executor.awaitTermination(1, TimeUnit.DAYS);

12．在控制台中显示程序结束的信息：

  System.out.printf("Main: End of the program.\n");
}

13．实现 showLog() 方法。该方法接收 Executor 作为参数，并输出线程池的大小、当前任务的数量以及执行器的状态：

private static void showLog(ThreadPoolExecutor executor) {
  System.out.printf("*********************");
  System.out.printf("Main: Executor Log");
  System.out.printf("Main: Executor: Core Pool Size: %d\n",
                    executor.getCorePoolSize());
  System.out.printf("Main: Executor: Pool Size: %d\n",
                    executor.getPoolSize());
  System.out.printf("Main: Executor: Active Count: %d\n",
                    executor.getActiveCount());
  System.out.printf("Main: Executor: Task Count: %d\n",
                    executor.getTaskCount());
  System.out.printf("Main: Executor: Completed Task Count: %d\n",
                    executor.getCompletedTaskCount());
  System.out.printf("Main: Executor: Shutdown: %s\n",
                    executor.isShutdown());
  System.out.printf("Main: Executor: Terminating: %s\n",
                    executor.isTerminating());
  System.out.printf("Main: Executor: Terminated: %s\n",
                    executor.isTerminated());
  System.out.printf("*********************\n");
}