This is part of a homework assignment. 

I am trying to make a `class` named `RomanNumeral` that has several methods. The first method, `RomanNumeral` checks whether a string `rn` is a Roman Numeral or not. The second method converts the Roman numeral into a decimal value. My problem lies with the rest of the methods. I am asked to create an override file for `.equals()`, `.compareTo()` and `toString()`. My question is how would I even begin doing this? What does it mean to override? Am I supposed to look at what they do, and emulate it? And if I am, where can look at the method that defines `.compareTo()` or `toString()`?

I can post my current code if it helps.