To get familiar with regex, formatted output and the Console class, I wrote a small program. You can use it learn regex. You can change it / play around with it to solidify your knowledge. And of course you can look for bugs/errors or suggest improvements.
The program asks for a string to search in and a regex pattern. It prints matches with start and end index and it prints the original string with the matches highlighted in bold.
I don't know if printing in bold works in a windows console, it's tested on Linux with bash.
The program comes with no license, so you are totally free to use/change it