java线程池模式--来自work thread模式的优化

在一篇文章中：工作线程模式，未考虑如下情况：

1.任务里很大时，工作线程不足时，导致客户端提交任务将阻塞的情况

2.任务里很少时，应该回收池中空闲的线程数量，回收资源

1.线程池类：

package threadpool;import java.util.LinkedList;import java.util.Vector;/** * 负责接收和存储任务，以及工作线程生命周期，主要职责如下： * 1.submit接口，提供给客户端 ，客户端 通过此接口提交任务 * 到线程池 *  * 2.shutdowm接口，关闭本池并释放池中资源 * @author lxb * */public class ThreadPool {private final LinkedList<TaskRequest> requestQueue; // 保存的请求队列private int count; // 请求队列中的请求数量private final LinkedList<WorkerThread> threadPool; // 工人线程池public ThreadPool(int threads) {this.requestQueue = new LinkedList<TaskRequest>();this.count = 0;threadPool = new LinkedList<WorkerThread>();for (int i = 0; i < threads; i++) { threadPool.addLast(new WorkerThread("Worker-" + i, this));}}/** * 当任务量很大时，添加工作线程 * @param thread */public void addWorkers(WorkerThread thread){threadPool.addLast(thread);thread.start();}/** * 当工作量很少时删除工作线程，节省开支 * @param count */public void deleteWorkers(int count){if(count > threadPool.size()){//这里不取=保证池中始终有一个线程在工作for(int i=0;i<count;i++){threadPool.pop();}}}/** * 开启工作线程 */public void startWorkers() {for (int i = 0; i < threadPool.size(); i++) {threadPool.get(i).start();}}public void stopAllWorkers(){for(int i=0;i<threadPool.size();i++){threadPool.get(i).stopThread();}}/** * 保存客户端发来的工作请求 *  * @param request * @throws InterruptedException  */public synchronized void putRequest(TaskRequest request) throws InterruptedException {// 当Request的数量大于或等于同时接受的数目时候，要等待while (!requestQueue.isEmpty()&&count >= requestQueue.size() ) {wait();}requestQueue.addLast(request);count++;notifyAll();}public synchronized TaskRequest takeRequest() throws InterruptedException {while (count <= 0) {wait();}TaskRequest request = requestQueue.pop();count--;notifyAll();return request;}}

2.工作线程：

package threadpool;/** * 工作线程，处理客户端发来的具体的工作请求 * @author lxb * */public class WorkerThread extends Thread{private final ThreadPool threadPool;private volatile boolean terminated = false;//停止请求标志public WorkerThread(String name,ThreadPool threadPool){super(name);this.threadPool = threadPool;}public void run() {        try {            while (!terminated) {                try {                                                           TaskRequest request = threadPool.takeRequest();                        request.execute();                                          } catch (InterruptedException e) {                    terminated = true;                }                                                           }        } finally {            System.out.println(Thread.currentThread().getName() + " is terminated.");        }    }    public void stopThread() {        terminated = true;        interrupt();    }}

3.工作请求类：

package threadpool;import java.util.Random;/** * 任务请求实体 * @author lxb * */public class TaskRequest {private final String name;      private final int number;       private static final Random random = new Random();    public TaskRequest(String name, int number) {        this.name = name;        this.number = number;    }    public void execute() {        System.out.println(Thread.currentThread().getName() + " executes " + this);        try {            Thread.sleep(random.nextInt(1000));        } catch (InterruptedException e) {        }    }    public String toString() {        return "[ Request from " + name + " No." + number + " ]";    }}

4.客户端线程：主要提交任务到线程池中去

package threadpool;import java.util.Random;/** * 不停的发送请求给工人类 *  * 1.创建请求实例，并将实例发送给管理工人线程的类 *  * @author lxb * */public class ClientThread extends Thread {private final ThreadPool channel;private static final Random random = new Random();private volatile boolean terminated = false; // 停止请求标志public ClientThread(String name, ThreadPool channel) {super(name);this.channel = channel;}public void run() {try {for (int i = 0; !terminated; i++) {try {TaskRequest request = new TaskRequest(getName(), i);channel.putRequest(request);Thread.sleep(random.nextInt(1000));} catch (InterruptedException e) {terminated = true;}}} finally {System.out.println(Thread.currentThread().getName()+ " is terminated.");}}public void stopThread() {terminated = true;interrupt();}}

6.测试类：

package threadpool;public class Main {public static void main(String[] args) {// TODO Auto-generated method stub ThreadPool channel = new ThreadPool(5);   // Worker Thread数量         channel.startWorkers();                  ClientThread alice = new ClientThread("Alice", channel);         ClientThread bobby = new ClientThread("Bobby", channel);         ClientThread chris = new ClientThread("Chris", channel);         alice.start();         bobby.start();         chris.start();         try {             Thread.sleep(5000);         } catch (InterruptedException e) {         }         alice.stopThread();         bobby.stopThread();         chris.stopThread();         channel.stopAllWorkers();}}