ThreadPoolTest.java

import java.util.concurrent.*;

public class ThreadPoolTest {

    public static void main(String[] args) {
        BlockingQueue<Runnable> queue = new SynchronousQueue<>();
        ExecutorService threadPool = new LoggingThreadPoolExecutor(1, 10, 30, TimeUnit.SECONDS, queue, new BlockingRejectedExecutionHandler());

        for (int i = 0; i < 1000; i++) {
            threadPool.submit(() -> {
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            });
        }

        threadPool.shutdown();
    }

    static class LoggingThreadPoolExecutor extends ThreadPoolExecutor {

        public LoggingThreadPoolExecutor(int corePoolSize, int maximumPoolSize, long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue, RejectedExecutionHandler handler) {
            super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue, handler);
        }

        @Override
        protected void beforeExecute(Thread t, Runnable r) {
            System.out.println("pool size: " + getPoolSize());
        }
    }

    static class BlockingRejectedExecutionHandler implements RejectedExecutionHandler {

        @Override
        public final void rejectedExecution(final Runnable r, final ThreadPoolExecutor executor) {
            try {
                executor.getQueue().put(r);
            } catch (InterruptedException e) {
                throw new RejectedExecutionException("Interrupted while waiting to put the element", e);
            }
        }

    }

}