public class DefaultThreadPool implements ThreadPool{//线程池最大限制数

private static final int MAX_WORKER_NUMBERS = 10;//线程池默认的数量

private static final int DEFAULT_WORKER_NUMBERS= 5;//线程池最小数量

private static final int MIN_WORKER_NUMBERS = 1;//这是一个任务列表，将会向里面插入任务

private final LinkedList jobs = new LinkedList() ;//工作者列表

private final List workers = Collections.synchronizedList(new ArrayList()) ;//工作者线程的数量

private int workerNum =DEFAULT_WORKER_NUMBERS ;//线程编号生成

private AtomicLong threadNum = newAtomicLong() ;publicDefaultThreadPool(){

initializeWorkers(DEFAULT_WORKER_NUMBERS);

}public DefaultThreadPool(intinitSize){

workerNum= initSize > MAX_WORKER_NUMBERS ?MAX_WORKER_NUMBERS :

initSize< MIN_WORKER_NUMBERS ?MIN_WORKER_NUMBERS : initSize ;

initializeWorkers(workerNum);

}private void initializeWorkers(intnum){for(int i = 0 ; i < num ; i++){

Worker worker= newWorker() ;

workers.add(worker) ;

Thread t= new Thread(worker, "ThreadPool-worker-"+threadNum.incrementAndGet()) ;

t.start();

}

}

@Overridepublic voidexecute(Task task) {if(task!=null){synchronized(jobs){

jobs.addLast(task);//通知

jobs.notify();

}

}

}

@Overridepublic voidshutdown() {for(Worker worker : workers){

worker.shutdown();

}

}

@Overridepublic void addWorker(intnum) {//这里是否应该选择workers为监视器锁

synchronized(workers){//判断新增的数量是否超出线程池的内置规则

if(num+this.workerNum >MAX_WORKER_NUMBERS){

num= MAX_WORKER_NUMBERS - this.workerNum ;

}

initializeWorkers(num);this.workerNum +=num ;

}

}

@Overridepublic void removeWorker(intnum) {synchronized(workers){if(num >= this.workerNum){throw new IllegalArgumentException("beyond workNum") ;

}for(int i = 0 ; i < num ; i++){

Worker worker=workers.get(i);if(workers.remove(worker)){

worker.shutdown();

}

}this.workerNum -=num ;

}

}

@Overridepublic intgetTaskSize() {returnjobs.size();

}class Worker implementsRunnable{private volatile booleanrunning ;

@Overridepublic voidrun() {while(running){

Task job= null;synchronized(jobs){//如果任务列表是空的，那么就wait

if(jobs.isEmpty()){try{

jobs.wait();

}catch(InterruptedException e) {//感知到外部对WorderThread的中断操作。返回

Thread.currentThread().interrupt();return;

}

}

job=jobs.removeFirst() ;

}if(job!=null){try{

job.run();

}catch(Exception e) {//忽略job执行中的exception

}

}

}//while end

}//run end

public voidshutdown(){

running= false;

}

}

}