JAvaカスタムスレッドプールの実装
8906 ワード
JAvaカスタムスレッドプールの実装
スレッドプールインタフェースの定義
スレッドプールインタフェースのデフォルト実装
例「Java同時作成アート」4.4.3スレッドプール技術とその例
スレッドプールインタフェースの定義
public interface ThreadPool<Job extends Runnable> {
// Job
void execute(Job job);
//
void shutdown();
//
void addWorkers(int num);
//
void removeWorker(int num);
//
int getJobSize();
}
スレッドプールインタフェースのデフォルト実装
public class DefaultThreadPool<Job extends Runnable> implements ThreadPool<Job> {
//
private static int MAX_WORKER_NUMBERS = 10;
//
private static int DEFAULT_WORKER_NUMBERS = 5;
//
private static int MIN_WORKER_NUMBERS = 1;
//
private final LinkedList jobs = new LinkedList<>();
//
private final List workers = Collections.synchronizedList(new ArrayList<>());
//
private int workerNum = DEFAULT_WORKER_NUMBERS;
private AtomicLong threadNum = new AtomicLong();
public DefaultThreadPool() {
initializeWorkers(DEFAULT_WORKER_NUMBERS);
}
public DefaultThreadPool(int num) {
workerNum = num > MAX_WORKER_NUMBERS ? MAX_WORKER_NUMBERS : num < MIN_WORKER_NUMBERS ? MIN_WORKER_NUMBERS : num;
initializeWorkers(workerNum);
}
//
private void initializeWorkers(int num) {
for (int i = 0; i < num; i++) {
Worker worker = new Worker();
workers.add(worker);
Thread thread = new Thread(worker, "ThreadPool-Worker-" + threadNum.incrementAndGet());
thread.start();
}
}
@Override
public void execute(Job job) {
if (job != null) {
synchronized (jobs) {
//
jobs.addLast(job);
jobs.notify();
}
}
}
@Override
public void shutdown() {
workers.forEach(Worker::shutdown);
}
@Override
public void addWorkers(int num) {
synchronized (jobs) {
// worker
if (num + this.workerNum > MAX_WORKER_NUMBERS) {
num = MAX_WORKER_NUMBERS - this.workerNum;
}
initializeWorkers(num);
this.workerNum += num;
}
}
@Override
public void removeWorker(int num) {
synchronized (jobs) {
if (num >= this.workerNum) {
throw new IllegalArgumentException("beyond workNum");
}
// worker
int count = 0;
while (count < num) {
Worker worker = workers.get(count);
if (workers.remove(worker)) {
worker.shutdown();
count++;
}
}
this.workerNum -= count;
}
}
@Override
public int getJobSize() {
return jobs.size();
}
//
class Worker implements Runnable {
//
private volatile boolean running = true;
@Override
public void run() {
while (running) {
Job job;
synchronized (jobs) {
while (jobs.isEmpty()) {
try {
jobs.wait();
} catch (InterruptedException e) {
// WorkerThread ,
Thread.currentThread().interrupt();
return;
}
}
job = jobs.removeFirst();
}
if (job != null) {
try {
job.run();
} catch (Exception ex) {
// job
}
}
}
}
public void shutdown() {
running = false;
}
}
}
例「Java同時作成アート」4.4.3スレッドプール技術とその例