線程池通俗的描述就是預先創建若幹空閑線程 等到需要用多線程去處理事務的時候去喚醒某些空閑線程執行處理任務 這樣就省去了頻繁創建線程的時間 因為頻 繁創建線程是要耗費大量的CPU資源的 如果壹個應用程序需要頻繁地處理大量並發事務 不斷的創建銷毀線程往往會大大地降低系統的效率 這時候線程池就派 上用場了
本文旨在使用Java語言編寫壹個通用的線程池 當需要使用線程池處理事務時 只需按照指定規範封裝好事務處理對象 然後用已有的線程池對象去自動選擇空 閑線程自動調用事務處理對象即可 並實現線程池的動態修改（修改當前線程數 最大線程數等） 下面是實現代碼
//ThreadTask java
package polarman threadpool;
/** *//**
*線程任務
* @author ryang
*
*/
public interface ThreadTask {
public void run();
}
//PooledThread java
package polarman threadpool;
import java util Collection; import java util Vector;
/** *//**
*接受線程池管理的線程
* @author ryang
*
*/
public class PooledThread extends Thread {
protected Vector tasks = new Vector();
protected boolean running = false;
protected boolean stopped = false;
protected boolean paused = false;
protected boolean killed = false;
private ThreadPool pool;
public PooledThread(ThreadPool pool) { this pool = pool;
}
public void putTask(ThreadTask task) { tasks add(task);
}
public void putTasks(ThreadTask[] tasks) { for(int i= ; i<tasks length; i++) this tasks add(tasks[i]);
}
public void putTasks(Collection tasks) { this tasks addAll(tasks);
}
protected ThreadTask popTask() { if(tasks size() > ) return (ThreadTask)tasks remove( );
else
return null;
}
public boolean isRunning() {
return running;
}
public void stopTasks() {
stopped = true;
}
public void stopTasksSync() {
stopTasks();
while(isRunning()) { try {
sleep( );
} catch (InterruptedException e) {
}
}
}
public void pauseTasks() {
paused = true;
}
public void pauseTasksSync() {
pauseTasks();
while(isRunning()) { try {
sleep( );
} catch (InterruptedException e) {
}
}
}
public void kill() { if(!running)
interrupt();
else
killed = true;
}
public void killSync() {
kill();
while(isAlive()) { try {
sleep( );
} catch (InterruptedException e) {
}
}
}
public synchronized void startTasks() {
running = true;
this notify();
}
public synchronized void run() { try { while(true) { if(!running || tasks size() == ) { pool notifyForIdleThread(); //System out println(Thread currentThread() getId() + : 空閑 ); this wait(); }else {
ThreadTask task;
while((task = popTask()) != null) { task run(); if(stopped) {
stopped = false;
if(tasks size() > ) { tasks clear(); System out println(Thread currentThread() getId() + : Tasks are stopped );
break;
}
}
if(paused) {
paused = false;
if(tasks size() > ) { System out println(Thread currentThread() getId() + : Tasks are paused );
break;
}
}
}
running = false;
}
if(killed) {
killed = false;
break;
}
}
}catch(InterruptedException e) {
return;
}
//System out println(Thread currentThread() getId() + : Killed );
}
}
//ThreadPool java
package polarman threadpool;
import java util Collection; import java util Iterator; import java util Vector;
/** *//**
*線程池
* @author ryang
*
*/
public class ThreadPool {
protected int maxPoolSize;
protected int initPoolSize;
protected Vector threads = new Vector();
protected boolean initialized = false;
protected boolean hasIdleThread = false;
public ThreadPool(int maxPoolSize int initPoolSize) { this maxPoolSize = maxPoolSize; this initPoolSize = initPoolSize;
}
public void init() {
initialized = true;
for(int i= ; i<initPoolSize; i++) {
PooledThread thread = new PooledThread(this);
thread start(); threads add(thread);
}
//System out println( 線程池初始化結束 線程數= + threads size() + 最大線程數= + maxPoolSize);
}
public void setMaxPoolSize(int maxPoolSize) { //System out println( 重設最大線程數 最大線程數= + maxPoolSize); this maxPoolSize = maxPoolSize;
if(maxPoolSize < getPoolSize())
setPoolSize(maxPoolSize);
}
/** *//**
*重設當前線程數
* 若需殺掉某線程 線程不會立刻殺掉 而會等到線程中的事務處理完成* 但此方法會立刻從線程池中移除該線程 不會等待事務處理結束
* @param size
*/
public void setPoolSize(int size) { if(!initialized) {
initPoolSize = size;
return;
}else if(size > getPoolSize()) { for(int i=getPoolSize(); i<size && i<maxPoolSize; i++) {
PooledThread thread = new PooledThread(this);
thread start(); threads add(thread);
}
}else if(size < getPoolSize()) { while(getPoolSize() > size) { PooledThread th = (PooledThread)threads remove( ); th kill();
}
}
//System out println( 重設線程數 線程數= + threads size());
}
public int getPoolSize() { return threads size();
}
protected void notifyForIdleThread() {
hasIdleThread = true;
}
protected boolean waitForIdleThread() {
hasIdleThread = false;
while(!hasIdleThread && getPoolSize() >= maxPoolSize) { try { Thread sleep( ); } catch (InterruptedException e) {
return false;
}
}
return true;
}
public synchronized PooledThread getIdleThread() { while(true) { for(Iterator itr=erator(); itr hasNext();) { PooledThread th = (PooledThread)itr next(); if(!th isRunning())
return th;
}
if(getPoolSize() < maxPoolSize) {
PooledThread thread = new PooledThread(this);
thread start(); threads add(thread);
return thread;
}
//System out println( 線程池已滿 等待 );
if(waitForIdleThread() == false)
return null;
}
}
public void processTask(ThreadTask task) {
PooledThread th = getIdleThread();
if(th != null) { th putTask(task); th startTasks();
}
}
public void processTasksInSingleThread(ThreadTask[] tasks) {
PooledThread th = getIdleThread();
if(th != null) { th putTasks(tasks); th startTasks();
}
}
public void processTasksInSingleThread(Collection tasks) {
PooledThread th = getIdleThread();
if(th != null) { th putTasks(tasks); th startTasks();
}
}
}
下面是線程池的測試程序
//ThreadPoolTest java
import java io BufferedReader; import java io IOException; import java io InputStreamReader;
import polarman threadpool ThreadPool; import polarman threadpool ThreadTask;
public class ThreadPoolTest {
public static void main(String[] args) { System out println( quit 退出 ); System out println( task A 啟動任務A 時長為 秒 ); System out println( size 設置當前線程池大小為 ); System out println( max 設置線程池最大線程數為 ); System out println();
final ThreadPool pool = new ThreadPool( ); pool init();
Thread cmdThread = new Thread() { public void run() {
BufferedReader reader = new BufferedReader(new InputStreamReader(System in));
while(true) { try { String line = reader readLine(); String words[] = line split( ); if(words[ ] equalsIgnoreCase( quit )) { System exit( ); }else if(words[ ] equalsIgnoreCase( size ) && words length >= ) { try { int size = Integer parseInt(words[ ]); pool setPoolSize(size); }catch(Exception e) {
}
}else if(words[ ] equalsIgnoreCase( max ) && words length >= ) { try { int max = Integer parseInt(words[ ]); pool setMaxPoolSize(max); }catch(Exception e) {
}
}else if(words[ ] equalsIgnoreCase( task ) && words length >= ) { try { int timelen = Integer parseInt(words[ ]); SimpleTask task = new SimpleTask(words[ ] timelen * ); pool processTask(task); }catch(Exception e) {
}
}
} catch (IOException e) { e printStackTrace();
}
}
}
};
cmdThread start();
/**//*
for(int i= ; i< ; i++){
SimpleTask task = new SimpleTask( Task + i (i+ )* ); pool processTask(task);
}*/
}
}
class SimpleTask implements ThreadTask {
private String taskName;
private int timeLen;
public SimpleTask(String taskName int timeLen) { this taskName = taskName; this timeLen = timeLen;
}
public void run() { System out println(Thread currentThread() getId() +
: START TASK + taskName + );
try { Thread sleep(timeLen); } catch (InterruptedException e) {
}
System out println(Thread currentThread() getId() +
: END TASK + taskName + );
}
}
使用此線程池相當簡單 下面兩行代碼初始化線程池
ThreadPool pool = new ThreadPool( ); pool init();
要處理的任務實現ThreadTask 接口即可（如測試代碼裏的SimpleTask） 這個接口只有壹個方法run()
兩行代碼即可調用
lishixinzhi/Article/program/Java/hx/201311/27203