Java并發(fā)編程中使用Executors類創(chuàng)建和管理線程的用法

更新時間：2016年03月01日 08:51:43 作者：zhangjunhd

這篇文章主要介紹了Java并發(fā)編程中使用Executors類創(chuàng)建和管理線程的用法,文中舉了用其啟動線程和設(shè)置線程優(yōu)先級的例子,需要的朋友可以參考下

1. 類 Executors
Executors類可以看做一個“工具類”。援引JDK1.6 API中的介紹：
此包中所定義的 Executor、ExecutorService、ScheduledExecutorService、ThreadFactory 和 Callable 類的工廠和實用方法。此類支持以下各種方法：
（1）創(chuàng)建并返回設(shè)置有常用配置字符串的 ExecutorService 的方法。
（2）創(chuàng)建并返回設(shè)置有常用配置字符串的 ScheduledExecutorService 的方法。
（3）創(chuàng)建并返回“包裝的”ExecutorService 方法，它通過使特定于實現(xiàn)的方法不可訪問來禁用重新配置。
（4）創(chuàng)建并返回 ThreadFactory 的方法，它可將新創(chuàng)建的線程設(shè)置為已知的狀態(tài)。
（5）創(chuàng)建并返回非閉包形式的 Callable 的方法，這樣可將其用于需要 Callable 的執(zhí)行方法中。
通過這個類能夠獲得多種線程池的實例，例如可以調(diào)用newSingleThreadExecutor()獲得單線程的ExecutorService，調(diào) 用newFixedThreadPool()獲得固定大小線程池的ExecutorService，等等。拿到ExecutorService可以做的事情就比較多了，最簡單的是用它來執(zhí)行Runnable對象，也可以執(zhí)行一些實現(xiàn)了Callable<T>的對象。用Thread的start()方法沒有返回值，如果該線程執(zhí)行的方法有返回值那用ExecutorService就再好不過了，可以選擇submit()、invokeAll()或者 invokeAny()，根據(jù)具體情況選擇合適的方法即可。
此類中提供的一些方法有：
1.1 public static ExecutorService newCachedThreadPool()
創(chuàng)建一個可根據(jù)需要創(chuàng)建新線程的線程池，但是在以前構(gòu)造的線程可用時將重用它們。對于執(zhí)行很多短期異步任務(wù)的程序而言，這些線程池通?？商岣叱绦蛐阅堋?br />
1.2 public static ExecutorService newFixedThreadPool(int nThreads)
創(chuàng)建一個可重用固定線程數(shù)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()
創(chuàng)建一個使用單個 worker 線程的 Executor，以無界隊列方式來運行該線程。

這三個方法都可以配合接口ThreadFactory的實例一起使用。并且返回一個ExecutorService接口的實例。
2. 接口 ThreadFactory
根據(jù)需要創(chuàng)建新線程的對象。使用線程工廠就無需再手工編寫對 new Thread 的調(diào)用了，從而允許應(yīng)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(xiàn)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.創(chuàng)建標準線程池啟動線程
4.1 提供一個簡單的實現(xiàn)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(yīng)的創(chuàng)建和執(zhí)行信息。

4.2使用CachedThreadPool啟動線程
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(jié)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啟動線程

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(jié)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啟動線程
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(jié)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
我們試圖給線程加入daemon和priority的屬性設(shè)置。
5.1設(shè)置后臺線程屬性
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(shè)置優(yōu)先級屬性
最高優(yōu)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(yōu)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啟動帶有屬性設(shè)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(jié)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)

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