Java实现自定义线程池
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ThreadPool
public interface ThreadPool {
void execute(Runnable runnable);
void shutdown();
int getInitSize();
int getMaxSize();
int getCoreSize();
int getQueueSize();
int getActiveCount();
boolean isShutdown();
}
RunnableQueue
public interface RunnableQueue {
void offer(Runnable runnable);
Runnable take() throws InterruptedException;
int size();
}
ThreadFactory
public interface ThreadFactory {
Thread createThread(Runnable r);
}
DennyPolicy
public interface DennyPolicy {
void reject(Runnable r, ThreadPool pool);
class DiscardPolicy implements DennyPolicy {
@Override
public void reject(Runnable r, ThreadPool pool) {
// do nothing
}
}
class AbortPolicy implements DennyPolicy {
@Override
public void reject(Runnable r, ThreadPool pool) {
throw new RejectedExecutionException();
}
}
class RunnerDenyPolicy implements DennyPolicy {
@Override
public void reject(Runnable r, ThreadPool pool) {
if (!pool.isShutdown()) {
r.run();
}
}
}
}
RunnableDenyException
public class RunnableDenyException extends RuntimeException {
public RunnableDenyException(String message) {
super(message);
}
}
InternalTask
public class InternalTask implements Runnable{
private final RunnableQueue runnableQueue;
private volatile boolean running = true;
public InternalTask(RunnableQueue runnableQueue) {
this.runnableQueue = runnableQueue;
}
@Override
public void run() {
while (running && !Thread.currentThread().isInterrupted()) {
try {
Runnable task = runnableQueue.take();
task.run();
} catch (InterruptedException e) {
running = false;
break;
}
}
}
public void stop() {
running = false;
}
}
LinkedRunnableQueue
public class LinkedRunnableQueue implements RunnableQueue {
private final int limit;
private final DennyPolicy dennyPolicy;
private final LinkedList<Runnable> runnableList = new LinkedList<>();
private final ThreadPool threadPool;
public LinkedRunnableQueue(final int limit, final DennyPolicy dennyPolicy, ThreadPool threadPool) {
this.limit = limit;
this.dennyPolicy = dennyPolicy;
this.threadPool = threadPool;
}
@Override
public void offer(Runnable runnable) {
synchronized (runnableList) {
if (runnableList.size() >= limit) {
dennyPolicy.reject(runnable, threadPool);
} else {
runnableList.add(runnable);
runnableList.notify();
}
}
}
@Override
public Runnable take() throws InterruptedException {
synchronized (runnableList) {
while (runnableList.isEmpty()) {
try {
runnableList.wait();
} catch (InterruptedException e) {
throw e;
}
}
}
return runnableList.removeFirst();
}
@Override
public int size() {
synchronized (runnableList) {
return runnableList.size();
}
}
}
BasicThreadPool
public class BasicThreadPool extends Thread implements ThreadPool {
private final int initSize;
private final int maxSize;
private final int coreSize;
private int activeCount;
private final ThreadFactory threadFactory;
private final RunnableQueue runnableQueue;
private volatile boolean isShutdown = false;
private final Queue<ThreadTask> threadQueue = new ArrayDeque<ThreadTask>();
private final static DennyPolicy DEFAULT_DENNY_POLICY = new DennyPolicy.DiscardPolicy();
private final static ThreadFactory DEFAULT_THREAD_FACTORY = new DefaultThreadFactory();
private final long keepAliveTime;
private final TimeUnit timeUnit;
public BasicThreadPool(int initSize, int maxSize, int coreSize, int queueSize) {
this(initSize, maxSize, coreSize, DEFAULT_THREAD_FACTORY, queueSize, DEFAULT_DENNY_POLICY, 10, TimeUnit.SECONDS);
}
public BasicThreadPool(int initSize, int maxSize, int coreSize, ThreadFactory threadFactory, int queueSize, DennyPolicy dennyPolicy, long keepAliveTime, TimeUnit unit) {
this.initSize = initSize;
this.maxSize = maxSize;
this.coreSize = coreSize;
this.threadFactory = threadFactory;
this.runnableQueue = new LinkedRunnableQueue(queueSize, dennyPolicy, this);
this.keepAliveTime = keepAliveTime;
this.timeUnit = unit;
this.init();
}
private void init() {
start();
for (int i = 0; i < initSize; i++) {
newThread();
}
}
private void newThread() {
InternalTask internalTask = new InternalTask(runnableQueue);
Thread thread = this.threadFactory.createThread(internalTask);
ThreadTask threadTask = new ThreadTask(thread, internalTask);
threadQueue.offer(threadTask);
this.activeCount++;
thread.start();
}
private void removeThread() {
ThreadTask threadTask = threadQueue.remove();
threadTask.internalTask.stop();
this.activeCount--;
}
@Override
public void run() {
while (!isShutdown && !isInterrupted()) {
try {
timeUnit.sleep(keepAliveTime);
} catch (InterruptedException e) {
isShutdown = true;
break;
}
synchronized (this) {
if (isShutdown) {
break;
}
if (runnableQueue.size() > 0 && activeCount < coreSize) {
for (int i = initSize; i < coreSize; i++) {
newThread();
}
continue;
}
if (runnableQueue.size() > 0 && activeCount < maxSize) {
for (int i = coreSize; i < maxSize; i++) {
newThread();
}
}
if (runnableQueue.size() == 0 && activeCount > coreSize) {
for (int i = coreSize; i < activeCount; i++) {
removeThread();
}
}
}
}
}
private static class ThreadTask {
Thread thread;
InternalTask internalTask;
public ThreadTask(Thread thread, InternalTask internalTask) {
this.thread = thread;
this.internalTask = internalTask;
}
}
@Override
public void execute(Runnable runnable) {
if (this.isShutdown) {
throw new IllegalStateException("ThreadPool is closed");
}
this.runnableQueue.offer(runnable);
}
@Override
public void shutdown() {
synchronized (this) {
if (isShutdown) {
return;
}
isShutdown = true;
threadQueue.forEach(threadTask -> {
threadTask.internalTask.stop();
threadTask.thread.interrupt();
});
this.interrupt();
}
}
@Override
public int getInitSize() {
if (isShutdown) {
throw new IllegalStateException("ThreadPool is closed");
}
return this.initSize;
}
@Override
public int getMaxSize() {
if (isShutdown) {
throw new IllegalStateException("ThreadPool is closed");
}
return this.maxSize;
}
@Override
public int getCoreSize() {
if (isShutdown) {
throw new IllegalStateException("ThreadPool is closed");
}
return this.coreSize;
}
@Override
public int getQueueSize() {
if (isShutdown) {
throw new IllegalStateException("ThreadPool is closed");
}
return runnableQueue.size();
}
@Override
public int getActiveCount() {
synchronized (this) {
return activeCount;
}
}
@Override
public boolean isShutdown() {
return this.isShutdown;
}
private static class DefaultThreadFactory implements ThreadFactory {
private static final AtomicInteger GROUP_COUNTER = new AtomicInteger(1);
private static final ThreadGroup group = new ThreadGroup("MyThreadPool" + GROUP_COUNTER.getAndDecrement());
private static final AtomicInteger COUNTER = new AtomicInteger(1);
@Override
public Thread createThread(Runnable runnable) {
return new Thread(group, runnable, "thread-pool-" + COUNTER.getAndDecrement());
}
}
}
ThreadPoolTest
public class ThreadPoolTest {
public static void main(String[] args) throws InterruptedException {
final BasicThreadPool threadPool = new BasicThreadPool(2, 6, 4, 1000);
for (int i = 0; i < 20; i++) {
threadPool.execute(() -> {
try {
TimeUnit.SECONDS.sleep(10);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
}
for (; ; ) {
System.out.println("getActiveCount() = " + threadPool.getActiveCount());
System.out.println("getQueueSize() = " + threadPool.getQueueSize());
System.out.println("getCoreSize() = " + threadPool.getCoreSize());
System.out.println("getMaxsize() = " + threadPool.getMaxSize());
System.out.println("=============================================");
TimeUnit.SECONDS.sleep(5);
}
}
}
运行结果
getActiveCount() = 2
getQueueSize() = 18
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 2
getQueueSize() = 18
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 4
getQueueSize() = 14
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 4
getQueueSize() = 14
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 6
getQueueSize() = 8
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 6
getQueueSize() = 8
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 6
getQueueSize() = 2
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 6
getQueueSize() = 2
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 5
getQueueSize() = 0
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 5
getQueueSize() = 0
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 4
getQueueSize() = 0
getCoreSize() = 4
getMaxsize() = 6
=============================================
getActiveCount() = 4
getQueueSize() = 0
getCoreSize() = 4
getMaxsize() = 6
=============================================
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