工厂设计模式是Java中最常用的设计模式之一。它是一种创建型设计模式,能够用于创建一个或多个类所需要的对象。有了这个工厂,我们就能集中的创建对象。
集中创建方式给我们带来了一些好处,例如:
1. 能够很容易的改变类创建的对象或者创建对象的方式;
2. 能够很容易限制对象的创建,例如:我们只能为a类创建N个对象;
3. 能够很容易的生成有关对象创建的统计数据。
在Java中,我们通常使用两种方式来创建线程:继承Thread类和实现Runnable接口。Java还提供了一个接口,既ThreadFactory接口,用于创建你自己的线程对象工厂。
很多类中,例如:ThreadPoolExecutor,使用构造函数来接收ThreadFactory来作为参数。这个工厂参数将会在程序执行时创建新的线程。使用ThreadFactory,你能够自定义执行程序如何创建线程,例如为线程定义适当的名称、优先级,或者你甚至可以将它设定为守护线程。
ThreadFactory例子
在这个例子中,我们将学习如何通过实现一个ThreadFactory接口来创建一个有个性化名称的线程对象,同时,我们保存了线程对象的创建信息。
Task.java
1. class Task implements Runnable
2. {
3. @Override
4. public void run()
5. {
6. try
7. {
8. TimeUnit.SECONDS.sleep(2);
9. } catch (InterruptedException e)
10. {
11. e.printStackTrace();
12. }
13. }
14. }
CustomThreadFactory.java
1. <span style="font-size:18px;">public class CustomThreadFactory implements ThreadFactory
2. {
3. private int counter;
4. private String name;
5. private List<String> stats;
6.
7. public CustomThreadFactory(String name)
8. {
9. counter = 1;
10. this.name = name;
11. stats = new ArrayList<String>();
12. }
13.
14. @Override
15. public Thread newThread(Runnable runnable)
16. {
17. Thread t = new Thread(runnable, name + "-Thread_" + counter);
18. counter++;
19. stats.add(String.format("Created thread %d with name %s on %s \n", t.getId(), t.getName(), new Date()));
20. return t;
21. }
22.
23. public String getStats()
24. {
25. StringBuffer buffer = new StringBuffer();
26. Iterator<String> it = stats.iterator();
27. while (it.hasNext())
28. {
29. buffer.append(it.next());
30. }
31. return buffer.toString();
32. }
33. }</span>
为了使用上面的线程工厂,请看下面的执行程序:
1. <span style="font-size:18px;">public static void main(String[] args)
2. {
3. CustomThreadFactory factory = new CustomThreadFactory("CustomThreadFactory");
4. Task task = new Task();
5. Thread thread;
6. System.out.printf("Starting the Threads\n\n");
7. for (int i = 1; i <= 10; i++)
8. {
9. thread = factory.newThread(task);
10. thread.start();
11. }
12. System.out.printf("All Threads are created now\n\n");
13. System.out.printf("Give me CustomThreadFactory stats:\n\n" + factory.getStats());
14. }</span>
程序执行结果:
1. <span style="font-size:18px;">Output :
2.
3. Starting the Threads
4.
5. All Threads are created now
6.
7. Give me CustomThreadFactory stats:
8.
9. Created thread 9 with name CustomThreadFactory-Thread_1 on Tue Jan 06 13:18:04 IST 2015
10. Created thread 10 with name CustomThreadFactory-Thread_2 on Tue Jan 06 13:18:04 IST 2015
11. Created thread 11 with name CustomThreadFactory-Thread_3 on Tue Jan 06 13:18:04 IST 2015
12. Created thread 12 with name CustomThreadFactory-Thread_4 on Tue Jan 06 13:18:04 IST 2015
13. Created thread 13 with name CustomThreadFactory-Thread_5 on Tue Jan 06 13:18:04 IST 2015
14. Created thread 14 with name CustomThreadFactory-Thread_6 on Tue Jan 06 13:18:04 IST 2015
15. Created thread 15 with name CustomThreadFactory-Thread_7 on Tue Jan 06 13:18:04 IST 2015
16. Created thread 16 with name CustomThreadFactory-Thread_8 on Tue Jan 06 13:18:04 IST 2015
17. Created thread 17 with name CustomThreadFactory-Thread_9 on Tue Jan 06 13:18:04 IST 2015
18. Created thread 18 with name CustomThreadFactory-Thread_10 on Tue Jan 06 13:18:04 IST 2015</span>
上面的代码中,ThreadFactory接口只有一个叫做newThread()的方法,它接收一个Runnable对象作为参数,同时返回一个Thread对象。当你实现ThreadFactory接口时,你必须重写这个方法。