最近写了一个 HTTP 代理服务器,发现访问网页时建立的连接很多,消耗的线程也非常的多,对于系统是
一个不小的开销.而且这些线程存在的时间都很短,99%以上的线程存在的时间都在毫秒的等级,相对来说
线程的建立的注销就占了绝大部分的CPU时间.
因此,在网上搜了一下线程池的资料,发现里面的东西不是太大太复杂,就是写得太烂,根本没有一点专业
水准.
没办法,只好自己简单的学习了一下 wait()/notify()机制,写了一个很小的线程池.
代码如下(一共2个类):
/*
*一个简单的线程池 ThreadPool .Java
*/
public class ThreadPool {
//以下是配置信息,可以更改
static int MAX_THREAD = 1000; //未使用
static int MIN_THREAD = 14;
static int id = 1; //线程 ID 号,主要用于监视线程的工作情况
static private ThreadPool pool = new ThreadPool();
static public ThreadPool getThreadPool() {
return pool;
}
Stack<WorkThread> stack = new Stack<WorkThread>(MIN_THREAD);
private ThreadPool() {
}
synchronized public boolean putWorkThread(WorkThread wt) {
if(stack.size()<MIN_THREAD){
stack.push(wt);
return true;
} else {
return false;
}
}
synchronized public WorkThread getWorkThread() {
WorkThread wt = null;
if(stack.isEmpty()) {
wt = new WorkThread(this);
new Thread(wt,"线程ID:"+id).start();
id++;
} else {
wt = stack.pop();
}
return wt;
}
}
--------------------------------------------------------------------------
/*
*工作线程类 WorkThread.java
*/
public class WorkThread implements Runnable {
Object lock = new Object();
Runnable runner = null;
ThreadPool pool = null;
public WorkThread(ThreadPool pool) {
this.pool = pool;
}
public void start(Runnable r) {
runner = r;
synchronized(lock) {
lock.notify();
}
}
public void run() {
while(true) {
if(runner != null) {
runner.run();
runner = null; //及时回收资源
}
if(pool.putWorkThread(this)) {
System.out.println (Thread.currentThread().getName()+" 被回收!");
synchronized(lock) {
try {
lock.wait();
} catch (InterruptedException ie) {
System.out.println ("停止线程时出现异常");
}
}
} else {
System.out.println (Thread.currentThread().getName()+" 被丢弃!");
break;
}
}
}
}