《java编程思想》并发的小例子报错，CachedTreadPool

Question

最近看了下《java编程思想》中关于并发的小例子，结果发现书上的例子运行不了，很奇怪。是关于CachedTreadPool的。

LiftOff.java

 

 

 

public class LiftOff implements Runnable {
    protected int countDown = 10;
    private static int taskCount = 0;
    private final int id = taskCount++;

    public LiftOff() {
    }

    public LiftOff(int countDown) {
        this.countDown = countDown;
    }

    public String status() {
        return "#" + id + "(" + (countDown > 0 ? countDown : "Liftoff!") + "),";
    }

    @Override
    public void run() {
        while (countDown-- > 0) {
            System.out.println(status());
            Thread.yield();
        }
    }

}

 

CachedTreadPool.java

 

 

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class CachedTreadPool {
    public static void main(String[] args) {
        ExecutorService exec = Executors.newCachedThreadPool();
        for (int i = 0; i < 5; i++) {
            exec.execute(new LiftOff());
            exec.shutdown();
        }
    }
}

 运行后报错

 

java.util.concurrent.RejectedExecutionException
    at java.util.concurrent.ThreadPoolExecutor$AbortPolicy.rejectedExecution(ThreadPoolExecutor.java:1768)
    at java.util.concurrent.ThreadPoolExecutor.reject(ThreadPoolExecutor.java:767)
    at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:658)
    at com.test.thread.CachedTreadPool.main(CachedTreadPool.java:13)
#0(9),
#0(8),
#0(7),
#0(6),
#0(5),
#0(4),
#0(3),
#0(2),
#0(1),
#0(Liftoff!),

请教各位大侠是什么错

 

Answer 1

exec.shutdown(); 写在循环里面了, 所以第二次循环就不接受任务了