Here's an example of how to use the ThreadMonitor class from the Apache Commons IO library:

import org.apache.commons.io.ThreadMonitor;

public class Example {
    public static void main(String[] args) {
        ThreadMonitor monitor = new ThreadMonitor();
        Thread thread1 = new Thread(new MyRunnable());
        Thread thread2 = new Thread(new MyRunnable());
        monitor.addThread(thread1);
        monitor.addThread(thread2);
        thread1.start();
        thread2.start();
        monitor.start();
    }
}

class MyRunnable implements Runnable {
    public void run() {
        // code to be executed by the thread
    }
}

In this example, a ThreadMonitor object is created and two threads thread1 and thread2 are added to it. These threads are started and then the start() method of the ThreadMonitor object is called. The ThreadMonitor monitors the status of the added threads and if any of them terminates due to an exception, it will throw an IOException.

This class provides a way to monitor the status of multiple threads and wait for them to complete. It can be useful when you need to wait for a group of threads to complete, and you want to be notified if one of the threads throws an exception.

Note : ThreadMonitor is a class that is used to monitor the status of multiple threads and wait for them to complete. It is not present in org.apache.commons.io package and it is not part of any official release of Apache Commons IO.