Fix that Java: Challenge

In this series I am going to share short codes with well-known, or less well-known but common problems that we, developers face from time to time during our work.

The series is about learning the language, learning its features, functionalities, and limits. It is up to you how to do it!

I am going to post a code snippet with a hidden misfunctionality. Your challenge is to solve that keeping the rules and limitations that I attach to the snippet.