Class to demonstrate the use of Monitor

FindSlowCode.java

package example;

import java.util.concurrent.atomic.AtomicLong;
import java.util.logging.Logger;
import java.util.stream.Stream;

/**
 * Class to demonstrate the use of Monitor
 */
public class FindSlowCode {

    public static void main(String[] args) {
        new FindSlowCode().run();
    }

    private void run() {
        Monitor monitor = new Monitor(Thread.currentThread(), 8);
        Thread thread = new Thread(monitor, "MonitorThread");
        thread.setDaemon(true);
        thread.start();

        while(true) {
            monitor.reset();
            double x=0;
            for (int i = 0; i < 10_000; i++) {
                x += Math.sqrt(i);
                Logger.getLogger(getClass().getName()).fine("x=" + x);
            }
        }
    }

    public static class Monitor implements Runnable{
        private final Thread thread;
        private final AtomicLong startTime = new AtomicLong(Long.MAX_VALUE);
        private final int thresholdMS;

        public Monitor(Thread thread, int thresholdMS){
            this.thread = thread;
            this.thresholdMS = thresholdMS;
        }

        public void reset(){
            startTime.set(System.currentTimeMillis());
        }

        @Override
        public void run(){
            while(thread.isAlive()){
                long timeTaken = System.currentTimeMillis()-startTime.get();
                if(timeTaken > thresholdMS){
                    System.out.println(timeTaken + "----------------------------");
                    Stream.of(thread.getStackTrace()).forEach(System.out::println);
                }
                try {
                    Thread.sleep(thresholdMS/2);
                } catch (InterruptedException e) {
                    break;
                }
            }
        }
    }
}

Thanks for sharing. Looks very interesting, but in a multi threaded application it might be difficult to manage monitors as you might not have control of the thread which executes your critical sections of your code.