使用Executors建立和管理線程

1. 類 Executors

此類中提供的一些方法有：

1.1 public static ExecutorService newCachedThreadPool()

建立一個可根據須要建立新線程的線程池，可是在之前構造的線程可用時將重用它們。對於執行不少短時間異步任務的程序而言，這些線程池一般可提升程序性能。

 

1.2 public static ExecutorService newFixedThreadPool(int nThreads)

建立一個可重用固定線程數的線程池，以共享的無界隊列方式來運行這些線程。

 

1.3 public static ExecutorService newSingleThreadExecutor()

建立一個使用單個 worker 線程的 Executor，以無界隊列方式來運行該線程。

 

這三個方法均可以配合接口ThreadFactory的實例一塊兒使用。而且返回一個ExecutorService接口的實例。

2. 接口 ThreadFactory

根據須要建立新線程的對象。使用線程工廠就無需再手工編寫對 new Thread 的調用了，從而容許應用程序使用特殊的線程子類、屬性等等。

此接口最簡單的實現就是：

class SimpleThreadFactory implements ThreadFactory {    public Thread newThread(Runnable r) {      return new Thread(r);    }  }

3. 接口ExecutorService

該接口提供了管理終止的方法。

4.建立標準線程池啓動線程

4.1 提供一個簡單的實現Runnable接口的線程

MyThread.java

package  com.zj.concurrency.executors;   public   class  MyThread  implements  Runnable {      private   int   count  = 1,  number ;        public  MyThread( int  num) {         number  = num;        System. out .println( "Create Thread-"  +  number );     }        public   void  run() {         while  ( true ) {            System. out .println( "Thread-"  +  number  +  " run "  +  count + " time(s)" );             if  (++ count  == 3)                return ;        }     } }

這個線程會打印出相應的建立和執行信息。

 

4.2使用CachedThreadPool啓動線程

CachedThreadPool.java

package  com.zj.concurrency.executors; import  java.util.concurrent.ExecutorService; import  java.util.concurrent.Executors;   public   class  CachedThreadPool {      public   static   void  main(String[] args) {        ExecutorService exec = Executors. newCachedThreadPool();         for  ( int  i = 0; i < 5; i++)            exec.execute( new  MyThread(i));        exec.shutdown();     } }

結果：

Create Thread-0

Create Thread-1

Create Thread-2

Create Thread-3

Thread-0 run 1 time(s)

Thread-0 run 2 time(s)

Thread-1 run 1 time(s)

Thread-1 run 2 time(s)

Thread-2 run 1 time(s)

Thread-2 run 2 time(s)

Create Thread-4

Thread-4 run 1 time(s)

Thread-4 run 2 time(s)

Thread-3 run 1 time(s)

Thread-3 run 2 time(s)

 

4.3 使用FixedThreadPool啓動線程

FixedThreadPool.java

package  com.zj.concurrency.executors; import  java.util.concurrent.ExecutorService; import  java.util.concurrent.Executors;   public   class  FixedThreadPool {      public   static   void  main(String[] args) {        ExecutorService exec = Executors. newFixedThreadPool(2);         for  ( int  i = 0; i < 5; i++)            exec.execute( new  MyThread(i));        exec.shutdown();     } }

結果：

Create Thread-0

Create Thread-1

Create Thread-2

Create Thread-3

Create Thread-4

Thread-0 run 1 time(s)

Thread-0 run 2 time(s)

Thread-2 run 1 time(s)

Thread-2 run 2 time(s)

Thread-3 run 1 time(s)

Thread-3 run 2 time(s)

Thread-4 run 1 time(s)

Thread-4 run 2 time(s)

Thread-1 run 1 time(s)

Thread-1 run 2 time(s)

 

4.4 使用SingleThreadExecutor啓動線程

SingleThreadExecutor.java

package  com.zj.concurrency.executors; import  java.util.concurrent.ExecutorService; import  java.util.concurrent.Executors;   public   class  SingleThreadExecutor {      public   static   void  main(String[] args) {        ExecutorService exec = Executors. newSingleThreadExecutor();         for  ( int  i = 0; i < 5; i++)            exec.execute( new  MyThread(i));        exec.shutdown();     } }

結果：

Create Thread-0

Create Thread-1

Create Thread-2

Create Thread-3

Create Thread-4

Thread-0 run 1 time(s)

Thread-0 run 2 time(s)

Thread-1 run 1 time(s)

Thread-1 run 2 time(s)

Thread-2 run 1 time(s)

Thread-2 run 2 time(s)

Thread-3 run 1 time(s)

Thread-3 run 2 time(s)

Thread-4 run 1 time(s)

Thread-4 run 2 time(s)

5.配合ThreadFactory接口的使用

咱們試圖給線程加入daemon和priority的屬性設置。

5.1設置後臺線程屬性

DaemonThreadFactory.java

package  com.zj.concurrency.executors.factory; import  java.util.concurrent.ThreadFactory;   public   class  DaemonThreadFactory  implements  ThreadFactory {      public  Thread newThread(Runnable r) {        Thread t =  new  Thread(r);        t.setDaemon( true );         return  t;     } }

 

5.2 設置優先級屬性

最高優先級MaxPriorityThreadFactory.java

package  com.zj.concurrency.executors.factory; import  java.util.concurrent.ThreadFactory;   public   class  MaxPriorityThreadFactory  implements  ThreadFactory {      public  Thread newThread(Runnable r) {        Thread t =  new  Thread(r);        t.setPriority(Thread. MAX_PRIORITY );         return  t;     } }

最低優先級MinPriorityThreadFactory.java

package  com.zj.concurrency.executors.factory; import  java.util.concurrent.ThreadFactory;   public   class  MinPriorityThreadFactory  implements  ThreadFactory {      public  Thread newThread(Runnable r) {        Thread t =  new  Thread(r);        t.setPriority(Thread. MIN_PRIORITY );         return  t;     } }

 

5.3啓動帶有屬性設置的線程

ExecFromFactory.java

package  com.zj.concurrency.executors; import  java.util.concurrent.ExecutorService; import  java.util.concurrent.Executors; import  com.zj.concurrency.executors.factory.DaemonThreadFactory; import  com.zj.concurrency.executors.factory.MaxPriorityThreadFactory; import  com.zj.concurrency.executors.factory.MinPriorityThreadFactory;   public   class  ExecFromFactory {      public   static   void  main(String[] args)  throws  Exception {        ExecutorService defaultExec = Executors. newCachedThreadPool();        ExecutorService daemonExec = Executors               . newCachedThreadPool( new  DaemonThreadFactory());        ExecutorService maxPriorityExec = Executors               . newCachedThreadPool( new  MaxPriorityThreadFactory());        ExecutorService minPriorityExec = Executors               . newCachedThreadPool( new  MinPriorityThreadFactory());         for  ( int  i = 0; i < 10; i++)            daemonExec.execute( new  MyThread(i));         for  ( int  i = 10; i < 20; i++)             if  (i == 10)               maxPriorityExec.execute( new  MyThread(i));             else   if  (i == 11)               minPriorityExec.execute ( new  MyThread(i));             else               defaultExec.execute( new  MyThread(i));     } }

結果：

Create Thread-0

Create Thread-1

Create Thread-2

Create Thread-3

Thread-0 run 1 time(s)

Thread-0 run 2 time(s)

Thread-1 run 1 time(s)

Thread-1 run 2 time(s)

Thread-2 run 1 time(s)

Thread-2 run 2 time(s)

Create Thread-4

Thread-4 run 1 time(s)

Thread-4 run 2 time(s)

Create Thread-5

Thread-5 run 1 time(s)

Thread-5 run 2 time(s)

Create Thread-6

Create Thread-7

Thread-7 run 1 time(s)

Thread-7 run 2 time(s)

Create Thread-8

Thread-8 run 1 time(s)

Thread-8 run 2 time(s)

Create Thread-9

Create Thread-10

Thread-10 run 1 time(s)

Thread-10 run 2 time(s)

Create Thread-11

Thread-9 run 1 time(s)

Thread-9 run 2 time(s)

Thread-6 run 1 time(s)

Thread-6 run 2 time(s)

Thread-3 run 1 time(s)

Thread-3 run 2 time(s)

Create Thread-12

Create Thread-13

Create Thread-14

Thread-12 run 1 time(s)

Thread-12 run 2 time(s)

Thread-13 run 1 time(s)

Thread-13 run 2 time(s)

Create Thread-15

Thread-15 run 1 time(s)

Thread-15 run 2 time(s)

Create Thread-16

Thread-16 run 1 time(s)

Thread-16 run 2 time(s)

Create Thread-17

Create Thread-18

Create Thread-19

Thread-14 run 1 time(s)

Thread-14 run 2 time(s)

Thread-17 run 1 time(s)

Thread-17 run 2 time(s)

Thread-18 run 1 time(s)

Thread-18 run 2 time(s)

Thread-19 run 1 time(s)

Thread-19 run 2 time(s)

Thread-11 run 1 time(s)

Thread-11 run 2 time(s)

本文出自 「i張俊」 博客，出處http://zhangjunhd.blog.51cto.com/113473/70068