易学笔记--从0开始学JAVA（个人纯手工笔记共享 免费！免费！免费！）--比直接看书快N倍的速度掌握知识点--第21章 并发（二）

第21章 并发/21.４ 终结任务/21.４.１ 装饰性花园－－花园门口人数计时器

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• 装饰性花园－－花园门口人数计时器

 

1. //: concurrency/OrnamentalGarden.java

   package concurrency;

   import java.util.concurrent.*;

   import java.util.*;

    

   import static net.mindview.util.Print.*;

    

   /**

    * 总的人数

    * @author Administrator

    *

    */

   class Count {

     private int count = 0;

     private Random rand = new Random(47);

     // Remove the synchronized keyword to see counting fail:

     public synchronized int increment() {

       int temp = count;

       if(rand.nextBoolean()) // Yield half the time

         Thread.yield();

       return (count = ++temp);

     }

     public synchronized int value() { return count; }

   }

    

   class Entrance implements Runnable {

     private static Count count = new Count();

    

     /**

      * 人数累加列表

      */

     private static List<Entrance> entrances =

       new ArrayList<Entrance>();

     /**

      * number:本线程人数

      */

     private int number = 0;

     // Doesn't need synchronization to read:

     private final int id;

     private static volatile boolean canceled = false;

     // Atomic operation on a volatile field:

     public static void cancel() { canceled = true; }

     public Entrance(int id) {

       this.id = id;

       // Keep this task in a list. Also prevents

       // garbage collection of dead tasks:

       entrances.add(this);

     }

     public void run() {

       while(!canceled) {

         synchronized(this) {

           ++number;

         }

         print(this + " Total: " + count.increment());

         try {

           TimeUnit.MILLISECONDS.sleep(100);

         } catch(InterruptedException e) {

           print("sleep interrupted");

         }

       }

       print("Stopping " + this);

   //    try {

   //    TimeUnit.SECONDS.sleep(1);

   // } catch (InterruptedException e) {

   //    // TODO Auto-generated catch block

   //    e.printStackTrace();

   // }

     }

     public synchronized int getValue() { return number; }

     public String toString() {

       return "Entrance " + id + ": " + getValue();

     }

     public static int getTotalCount() {

       return count.value();

     }

     /**

      * 汇总各个线程的值

      * @return

      */

     public static int sumEntrances() {

       int sum = 0;

       for(Entrance entrance : entrances)

         sum += entrance.getValue();

       return sum;

     }

   }

    

   public class OrnamentalGarden {

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

       ExecutorService exec = Executors.newCachedThreadPool();

       for(int i = 0; i < 5; i++)

         exec.execute(new Entrance(i));

       // Run for a while, then stop and collect the data:

       TimeUnit.SECONDS.sleep(1);

       /**

        * 发出取消操作

        */

       Entrance.cancel();

       exec.shutdownNow();

       /**

        * 在一定时间内等待run函数结束

        */

       if(!exec.awaitTermination(250, TimeUnit.MILLISECONDS))

         print("Some tasks were not terminated!");

       print("Total: " + Entrance.getTotalCount());

       print("Sum of Entrances: " + Entrance.sumEntrances());

     }

   } /* Output: (Sample)

   Entrance 0: 1 Total: 1

   Entrance 2: 1 Total: 3

   Entrance 1: 1 Total: 2

   Entrance 4: 1 Total: 5

   Entrance 3: 1 Total: 4

   Entrance 2: 2 Total: 6

   Entrance 4: 2 Total: 7

   Entrance 0: 2 Total: 8

   ...

   Entrance 3: 29 Total: 143

   Entrance 0: 29 Total: 144

   Entrance 4: 29 Total: 145

   Entrance 2: 30 Total: 147

   Entrance 1: 30 Total: 146

   Entrance 0: 30 Total: 149

   Entrance 3: 30 Total: 148

   Entrance 4: 30 Total: 150

   Stopping Entrance 2: 30

   Stopping Entrance 1: 30

   Stopping Entrance 0: 30

   Stopping Entrance 3: 30

   Stopping Entrance 4: 30

   Total: 150

   Sum of Entrances: 150

   *///:~

    

---

 

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