線程池

任何遊戲都至少需要運作兩個線程,主線程和gui線程 

而線程池是一個管理運作線程的有用工具,下面的代碼示範了一個線程池的實作方法~~ 

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(threadpool.java) 

import java.util.linkedlist; 

/** 

線程池是一組線程，限制執行任務的線程數 

*/ 

public class threadpool extends threadgroup { 

private boolean isalive; 

private linkedlist taskqueue; 

private int threadid; 

private static int threadpoolid; 

建立新的線程池，numthreads是池中的線程數 

public threadpool(int numthreads) { 

super("threadpool-" + (threadpoolid++)); 

setdaemon(true); 

isalive = true; 

taskqueue = new linkedlist(); 

for (int i=0; i<numthreads; i++) { 

new pooledthread().start(); 

} 

請求新任務。人物在池中下一空閑線程中運作，任務按收到的順序執行 

public synchronized void runtask(runnable task) { 

if (!isalive) { 

throw new illegalstateexception();//線程被關則抛出illegalstateexception異常 

if (task != null) { 

taskqueue.add(task); 

notify(); 

protected synchronized runnable gettask() 

throws interruptedexception 

{ 

while (taskqueue.size() == 0) { 

return null; 

wait(); 

return (runnable)taskqueue.removefirst(); 

關閉線程池，所有線程停止，不再執行任務 

public synchronized void close() { 

if (isalive) { 

isalive = false; 

taskqueue.clear(); 

interrupt(); 

關閉線程池并等待所有線程完成，執行等待的任務 

public void join() { 

//告訴等待線程線程池已關 

synchronized (this) { 

notifyall(); 

// 等待所有線程完成 

thread[] threads = new thread[activecount()]; 

int count = enumerate(threads); 

for (int i=0; i<count; i++) { 

try { 

threads[i].join(); 

catch (interruptedexception ex) { } 

用于進行任務的線程 

private class pooledthread extends thread { 

public pooledthread() { 

super(threadpool.this, 

"pooledthread-" + (threadid++)); 

public void run() { 

while (!isinterrupted()) { 

// 得到任務 

runnable task = null; 

task = gettask(); 

// 若gettask()傳回null或中斷，則關閉此線程并傳回 

if (task == null) { 

return; 

// 運作任務，吸收異常 

task.run(); 

catch (throwable t) { 

uncaughtexception(this, t); 

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要測試這個線程池，可以通過下面這個test程式！ 

(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"); 

" numtasks - integer: number of task to run."); 

" numthreads - integer: number of threads " + 

"in the thread pool."); 

int numtasks = integer.parseint(args[0]); 

int numthreads = integer.parseint(args[1]); 

// 生成線程池 

threadpool threadpool = new threadpool(numthreads); 

// 運作任務 

for (int i=0; i<numtasks; i++) { 

threadpool.runtask(createtask(i)); 

// 關閉線程池并等待所有任務完成 

threadpool.join(); 

一個簡單的任務(列印id) 

private static runnable createtask(final int taskid) { 

return new runnable() { 

system.out.println("task " + taskid + ": start"); 

// 增加耗時 

thread.sleep(500); 

system.out.println("task " + taskid + ": end"); 

}; 

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這樣的線程池可以在許多地方應用！