Java 并发编程之自定义线程池
Java juc About 6,753 words代码
- 核心线程
- 阻塞队列
- 拒绝策略
- 未实现线程
maxSize
功能
public class CustomThreadPool {
public static void main(String[] args) {
ThreadPool threadPool = new ThreadPool(1, 1000, TimeUnit.MILLISECONDS, 1, (queue, task) -> {
// 死等
// queue.put(task);
// 带超时时间
// queue.offer(task, 1500, TimeUnit.MILLISECONDS);
// 让调用者放弃任务执行
// System.out.println("放弃任务"); // 什么都不用做,表示放弃
// 让调用者抛出异常
// throw new RuntimeException("任务执行失败#" + task); // 抛出异常后,之后的任务的都不执行了
// 让调用者自己执行任务
task.run();
});
for (int i = 0; i < 3; i++) {
int finalI = i;
threadPool.execute(() -> {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(finalI);
});
}
}
}
@FunctionalInterface
interface RejectPolicy<T> {
void reject(BlockingQueue<T> queue, T task);
}
class ThreadPool {
// 任务队列
private final BlockingQueue<Runnable> taskQueue;
// 线程集合
private final HashSet<Worker> workers = new HashSet<>();
// 核心线程数
private final int coreSize;
// 获取任务的超时时间
private final long timeout;
private final TimeUnit timeUnit;
private final RejectPolicy<Runnable> rejectPolicy;
public void execute(Runnable task) {
synchronized (workers) {
// 当任务数没有超过 coreSize 交给 worker 执行
// 如果任务数超过 coreSize 加入任务队列暂存
if (workers.size() < coreSize) {
Worker worker = new Worker(task);
System.out.println("new worker#" + worker + ", task#" + task);
workers.add(worker);
worker.start();
} else {
taskQueue.tryPut(rejectPolicy, task);
}
}
}
public ThreadPool(int coreSize, long timeout, TimeUnit timeUnit, int queueCapacity, RejectPolicy<Runnable> rejectPolicy) {
this.coreSize = coreSize;
this.timeout = timeout;
this.timeUnit = timeUnit;
this.taskQueue = new BlockingQueue<>(queueCapacity);
this.rejectPolicy = rejectPolicy;
}
class Worker extends Thread {
private Runnable task;
public Worker(Runnable task) {
this.task = task;
}
@Override
public void run() {
// 当任务不为空,执行任务
// 当任务为空,从任务队列获取任务并执行
// while (task != null || (task = taskQueue.take()) != null) {
while (task != null || (task = taskQueue.poll(timeout, timeUnit)) != null) {
try {
System.out.println(Thread.currentThread() + ", task executing#" + task);
task.run();
} catch (Exception e) {
e.printStackTrace();
} finally {
task = null;
}
}
synchronized (workers) {
System.out.println("remove worker#" + this);
workers.remove(this);
}
}
}
}
class BlockingQueue<T> {
// 任务队列
private final Deque<T> queue = new ArrayDeque<>();
// 锁
private final ReentrantLock lock = new ReentrantLock();
// 生产者消费变量
private final Condition fullWaitSet = lock.newCondition();
// 消费者条件变量
private final Condition emptyWaitSet = lock.newCondition();
// 容量
private final int capacity;
public BlockingQueue(int capacity) {
this.capacity = capacity;
}
// 带超时的阻塞获取
public T poll(long timeout, TimeUnit unit) {
lock.lock();
try {
long nanos = unit.toNanos(timeout);
while (queue.isEmpty()) {
try {
if (nanos <= 0) {
return null;
}
nanos = emptyWaitSet.awaitNanos(nanos);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
T t = queue.removeFirst();
fullWaitSet.signal();
return t;
} finally {
lock.unlock();
}
}
// 阻塞添加
public T take() {
lock.lock();
try {
while (queue.isEmpty()) {
try {
emptyWaitSet.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
T t = queue.removeFirst();
fullWaitSet.signal();
return t;
} finally {
lock.unlock();
}
}
// 阻塞放入
public void put(T element) {
lock.lock();
try {
while (size() == capacity) {
try {
System.out.println("wait for adding task#" + element);
fullWaitSet.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("add task#" + element);
queue.addLast(element);
emptyWaitSet.signal();
} finally {
lock.unlock();
}
}
public boolean offer(T task, long timeout, TimeUnit timeUnit) {
lock.lock();
try {
long nanos = timeUnit.toNanos(timeout);
while (size() == capacity) {
try {
if (nanos <= 0) {
return false;
}
System.out.println("wait for adding task#" + task);
nanos = fullWaitSet.awaitNanos(nanos);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println("add task#" + task);
queue.addLast(task);
emptyWaitSet.signal();
return true;
} finally {
lock.unlock();
}
}
public int size() {
lock.lock();
try {
return queue.size();
} finally {
lock.unlock();
}
}
public void tryPut(RejectPolicy<T> rejectPolicy, T task) {
lock.lock();
try {
// 队列满
if (queue.size() == capacity) {
rejectPolicy.reject(this, task);
} else {// 有空闲
System.out.println("add task#" + task);
queue.addLast(task);
emptyWaitSet.signal();
}
} finally {
lock.unlock();
}
}
}
Views: 2,259 · Posted: 2021-11-09
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