How do I use one Java program, to monitor another Java program's output?

Question

Below is diagram that shows what I\'m trying to do : it is just 2 programs. One is a simple Child program that writes out integers every 2 seconds, line-by-line

Answer 1

You can use the directory watch service:

https://docs.oracle.com/javase/tutorial/essential/io/notification.html

You can configure a path or a file and register a watcher.

The watcher gets a notification every time a file is changed. You can store this timestamp of a notification for later use.

For details see my link above.

You may then use a Timer or a Thread to check last modification.