Java Multithreading - main thread stopped

Question

I have Java app which reads data from IoT devices. For I have example smart thermometer:

public class Thermometer{

    private final String ip;

    public Thermometer(String ip) {
        this.ip = ip;
    }

    public void startReading () {
        Thread readThread = new Thread(() -> {
            while (true) {
                try {
                    //reading, writing data to DB
                } catch (Exception e) {
                    //logging
                }
            }
        });
        readThread.start();
    }
}

In my main I add all my IoT devices and start their reading threads:

new Thermometer("192.168.1.100").startReading();
new Thermometer("192.168.1.101").startReading();

After a while (last time I've tryed it was about 12 hours) my main thread stops so all my threads stop too. My log file (log4j2) has single line about this:

com.foo.Main - null

Probably complete stack trace was printed to sys.err. I will try to catch it and update post.

Why does it happen? How can I start all my threads so they will run forever?

UPD. Main class:

public class Main {

    public static void main(String[] args) {
        new Thermometer("192.168.1.100").startReading();
        new Thermometer("192.168.1.101").startReading();
    }
}

UPD2. Starting script:

nohup java -Dlog4j.configurationFile=$PATH_TO_LOG4J2_XML -jar $PATH_TO_REEVE_JAR >> /home/buger/reeve/nohup.log 2>>&1 &
echo $! > $PATH_TO_PID
echo_and_log "Successfully started! PID = `cat $PATH_TO_PID`"

Answer 1

I think something happened to your reader threads. Maybe an exception , achem, an Error killed them. I suggest you to debug that.

Meanwhile, here is an example code that sort of proves my theory:

public class Main {

    public static void main(String[] args) {
        Thread thread1 = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("--> thread 1");
            }
        });
        Thread thread2 = new Thread(() -> {
            while (true) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println("--> thread 2");
            }
        });
        thread1.start();
        thread2.start();
        System.out.println("--> main thread about to finish");
    }

}

This produces the following output:

--> main thread about to finish
--> thread 2
--> thread 1
--> thread 1
--> thread 2
...