need decoding current java jar file for current project, reading existing coding, doing maintenance based on it

I am looking for a skilled Java developer who can decode and analyze the current java jar file of my project. The purpose of the jar file is user interface development, so understanding its coding is crucial for maintaining and enhancing the project.

Specifically, I have specific features and functions in mind that I would like to maintain and possibly enhance. Therefore, I need someone with experience in user interface development who can work with the existing coding to make the necessary updates and improvements. Coding size about 830KB, considered as small-medium project

As for the deadlines, they are flexible. I am looking for someone who can dedicate their time and expertise to this project and deliver high-quality results within a reasonable timeframe.

Skills and experience required:
- Strong proficiency in Java programming
- Expertise in user interface development
- Experience with decoding and analyzing java jar files
- Ability to understand and work with existing coding
- Attention to detail and ability to maintain and enhance specific features/functions