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任何游戏都至少需要运行两个线程,主线程和gui线程
而线程池是一个管理运行线程的有用工具,下面的代码示范了一个线程池的实现方法~~
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(threadpool.java)
import java.util.linkedlist;
/**
线程池是一组线程，限制执行任务的线程数
*/
public class threadpool extends threadgroup {
private boolean isalive;
private linkedlist taskqueue;
private int threadid;
private static int threadpoolid;
/**
创建新的线程池，numthreads是池中的线程数
*/
public threadpool(int numthreads) {
super("threadpool-" + (threadpoolid++));
setdaemon(true);
isalive = true;
taskqueue = new linkedlist();
for (int i=0; i<numthreads; i++) {
new pooledthread().start();
}
}
/**
请求新任务。人物在池中下一空闲线程中运行，任务按收到的顺序执行
*/
public synchronized void runtask(runnable task) {
if (!isalive) {
throw new illegalstateexception();//线程被关则抛出illegalstateexception异常
}
if (task != null) {
taskqueue.add(task);
notify();
}
}
protected synchronized runnable gettask()
throws interruptedexception
{
while (taskqueue.size() == 0) {
if (!isalive) {
return null;
}
wait();
}
return (runnable)taskqueue.removefirst();
}
/**
关闭线程池，所有线程停止，不再执行任务
*/
public synchronized void close() {
if (isalive) {
isalive = false;
taskqueue.clear();
interrupt();
}
}
/**
关闭线程池并等待所有线程完成，执行等待的任务
*/
public void join() {
//告诉等待线程线程池已关
synchronized (this) {
isalive = false;
notifyall();
}
// 等待所有线程完成
thread[] threads = new thread[activecount()];
int count = enumerate(threads);
for (int i=0; i<count; i++) {
try {
threads[i].join();
}
catch (interruptedexception ex) { }
}
}
/**
用于进行任务的线程
*/
private class pooledthread extends thread {
public pooledthread() {
super(threadpool.this,
"pooledthread-" + (threadid++));
}
public void run() {
while (!isinterrupted()) {
// 得到任务
runnable task = null;
try {
task = gettask();
}
catch (interruptedexception ex) { }
// 若gettask()返回null或中断，则关闭此线程并返回
if (task == null) {
return;
}
// 运行任务，吸收异常
try {
task.run();
}
catch (throwable t) {
uncaughtexception(this, t);
}
}
}
}
}
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要测试这个线程池，可以通过下面这个test程序！
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(threadpooltest.java)
public class threadpooltest {
public static void main(string[] args) {
if (args.length != 2) {
system.out.println("tests the threadpool task.");
system.out.println(
"usage: java threadpooltest numtasks numthreads");
system.out.println(
" numtasks – integer: number of task to run.");
system.out.println(
" numthreads – integer: number of threads " +
"in the thread pool.");
return;
}
int numtasks = integer.parseint(args[0]);
int numthreads = integer.parseint(args[1]);
// 生成线程池
threadpool threadpool = new threadpool(numthreads);
// 运行任务
for (int i=0; i<numtasks; i++) {
threadpool.runtask(createtask(i));
}
// 关闭线程池并等待所有任务完成
threadpool.join();
}
/**
一个简单的任务(打印id)
*/
private static runnable createtask(final int taskid) {
return new runnable() {
public void run() {
system.out.println("task " + taskid + ": start");
// 增加耗时
try {
thread.sleep(500);
}
catch (interruptedexception ex) { }
system.out.println("task " + taskid + ": end");
}
};
}
}
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这样的线程池可以在许多地方应用！
