How to create properties class handler with using default properties

Question

phew there are lots of questions from my side these days, but:

I'm looking for the best solution of how to handle properties file when one of them are missing, than use default values. I'm using:

serenity-bdd, selenium, java, maven.

My solution is:

1. Create Interface with constants
2. Create handler which is going to have at least 3 methods like, getDefaultProperties, getCustomProperties and last is method which should return list of properties, but if defaultValue != customValue than override and put to array and return, then I'm going to handle each parameter where I need.

Appreciate for advice,

Thank you.