工厂模式是面向对象编程世界中最有用的设计模式。
它是一个创新型的模式，目标是开发一个对象，这个对象的任务是去创建其他类对象。
1.容易改变对象的类或者创建这些对象的方式；
2.容易限制所创建的对象。例如，我们只能创建N个某类型的对象；
3.容易生成对象创建的统计数据；Java并发API提供了ThreadFactory接口以实现一个线程对象工厂。一些并发API高级工具都使用线程工厂去创建线程。
本例中，我们将学习如何去实现ThreadFactory接口去创建线程对象。
MyThreadFactory.java
package com.dylan.thread.ch1.c12.factory;
import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ThreadFactory;
/**
* Class that implements the ThreadFactory interface to
* create a basic thread factory
*
*/
public class MyThreadFactory implements ThreadFactory {
// Attributes to save the necessary data to the factory
private int counter;
private String name;
private List<String> stats;
/**
* Constructor of the class
* @param name Base name of the Thread objects created by this Factory
*/
public MyThreadFactory(String name){
counter=0;
this.name=name;
stats=new ArrayList<String>();
}
/**
* Method that creates a new Thread object using a Runnable object
* @param r: Runnable object to create the new Thread
*/
@Override
public Thread newThread(Runnable r) {
// Create the new Thread object
Thread t=new Thread(r,name+"-Thread_"+counter);
counter++;
// Actualize the statistics of the factory
stats.add(String.format("Created thread %d with name %s on %s\n",t.getId(),t.getName(),new Date()));
return t;
}
/**
* Method that returns the statistics of the ThreadFactory
* @return The statistics of the ThreadFactory
*/
public String getStats(){
StringBuffer buffer=new StringBuffer();
Iterator<String> it=stats.iterator();
while (it.hasNext()) {
buffer.append(it.next());
}
return buffer.toString();
}
}
Task.java
package com.dylan.thread.ch1.c12.task;
import java.util.concurrent.TimeUnit;
public class Task implements Runnable {
@Override
public void run() {
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
Main.java
package com.dylan.thread.ch1.c12.core;
import com.dylan.thread.ch1.c12.factory.MyThreadFactory;
import com.dylan.thread.ch1.c12.task.Task;
/**
* Main class of the example. Creates a Thread factory and creates ten
* Thread objects using that Factory
*
*/
public class Main {
/**
* Main method of the example. Creates a Thread factory and creates
* ten Thread objects using that Factory
* @param args
*/
public static void main(String[] args) {
// Creates the factory
MyThreadFactory factory=new MyThreadFactory("MyThreadFactory");
// Creates a task
Task task=new Task();
Thread thread;
// Creates and starts ten Thread objects
System.out.printf("Starting the Threads\n");
for (int i=0; i<10; i++){
thread=factory.newThread(task);
thread.start();
}
// Prints the statistics of the ThreadFactory to the console
System.out.printf("Factory stats:\n");
System.out.printf("%s\n",factory.getStats());
}
}
运行结果：
Starting the Threads Factory stats: Created thread 10 with name MyThreadFactory-Thread_0 on Sat May 05 16:34:56 CST 2018 Created thread 11 with name MyThreadFactory-Thread_1 on Sat May 05 16:34:56 CST 2018 Created thread 12 with name MyThreadFactory-Thread_2 on Sat May 05 16:34:56 CST 2018 Created thread 13 with name MyThreadFactory-Thread_3 on Sat May 05 16:34:56 CST 2018 Created thread 14 with name MyThreadFactory-Thread_4 on Sat May 05 16:34:56 CST 2018 Created thread 15 with name MyThreadFactory-Thread_5 on Sat May 05 16:34:56 CST 2018 Created thread 16 with name MyThreadFactory-Thread_6 on Sat May 05 16:34:56 CST 2018 Created thread 17 with name MyThreadFactory-Thread_7 on Sat May 05 16:34:56 CST 2018 Created thread 18 with name MyThreadFactory-Thread_8 on Sat May 05 16:34:56 CST 2018 Created thread 19 with name MyThreadFactory-Thread_9 on Sat May 05 16:34:56 CST 2018