一个带有线程序号池的ThreadFactory

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.concurrent.ConcurrentSkipListSet;
import java.util.concurrent.RejectedExecutionHandler;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.ThreadPoolExecutor;
/**
 *
 *
 * @author q4073
 * @date 2020-07-02 19:53
 */
public class SequentialThreadFactory implements ThreadFactory {
    private final static int INIT_MAX_SERIAL_NUMBER = 64;
    private final ConcurrentSkipListSet<Integer> serialNumberPool;
    private final int maxSerialNumber;
    private final String threadNamePrefix;
    private boolean daemon = false;
    public SequentialThreadFactory(String threadNamePrefix) {
        this(threadNamePrefix, INIT_MAX_SERIAL_NUMBER);
    }
    public SequentialThreadFactory(String threadNamePrefix, int expectantThreadCount) {
        this.threadNamePrefix = threadNamePrefix;
        serialNumberPool = new ConcurrentSkipListSet<>();
        maxSerialNumber = expectantThreadCount;
        for (int i = 0; i < maxSerialNumber; i++) {
            serialNumberPool.add(i);
        }
    }
    public SequentialThreadFactory withDaemon(boolean daemon) {
        this.daemon = daemon;
        return this;
    }
    public boolean isDaemon() {
        return daemon;
    }
    private synchronized void expand() {
        int newCount = maxSerialNumber * 2;
        for (int i = maxSerialNumber; i < newCount; i++) {
            serialNumberPool.add(i);
        }
    }
    @Override
    public Thread newThread(Runnable r) {
        Integer serialNumber = serialNumberPool.pollFirst();
        if (serialNumber == null) {
            expand();
            serialNumber = serialNumberPool.pollFirst();
            serialNumber = serialNumber == null ? 0 : serialNumber;
        }
        RunnableProxy proxy = new RunnableProxy(serialNumber, r);
        Thread t = new Thread(proxy, threadNamePrefix + serialNumber);
        t.setDaemon(daemon);
        return t;
    }
    static class LogRejectedHandler implements RejectedExecutionHandler {
        private static final Logger LOG = LoggerFactory.getLogger(LogRejectedHandler.class);
        @Override
        public void rejectedExecution(Runnable r, ThreadPoolExecutor executor) {
            String msg = "推送任务队列严重阻塞！推送任务已被丢弃: " + r.toString();
            LOG.error(msg);
        }
    }
    private class RunnableProxy implements Runnable {
        private final int serialNumber;
        private final Runnable runnable;
        RunnableProxy(int serialNumber, Runnable runnable) {
            this.serialNumber = serialNumber;
            this.runnable = runnable;
        }
        @Override
        public void run() {
            try {
                runnable.run();
            } finally {
                serialNumberPool.add(serialNumber);
            }
        }
    }
}