Java beginning from JDK 9 was Modularized and hence development has become easier since then. I will modularize your existing Java applications i.e. write code with modules approach. The application may be of any sort written in JDK 8 or prior. Support for legacy operations might depend on Java's features.
Your existing source code packages will be converted into modules, note that modules do not interfere in traditional package functionalities in any way, existing packages will work as they are. However modules restrict access to its files depending upon whether the file has been appropriately included and exported from the module.
The number of modules and their configuration will completely based on application requirements.
The code for modules written will be appropriately documented for utmost ease of maintenance in future scope following appropriate standards.