How to recursively load classes from a particular package

Question

I am creating a modular app. The following is my design:

my_app_package  
  PluginsLoader.java  
  plugins_package
    plugin_A  
      Start.java  
      plugin_a_inner_package_1  
      plugin_a_inner_package_2
      plugin_a_inner_package _3  
    plugin_B  
      Start.java  
      plugin_b_inner_package_1  
      plugin_b_inner_package_2  
    plugin_C  
      Start.java  
      plugin_c_inner_package_1  

I would like to recursively go through all the Start.java classes in the roots of plugins_package root packages, but not go through any of the pluginA, pluinB etc etc*_inner_packages.

How can I do this efficiently.

I know my_app_package.plugins_package.*.Start.java will not work, but it draws on the idea of what I'm seeking.

Thank you all in advance.

UPDATE

I would like to recursively go through all the Start.java classes in the roots of plugins_package packages, but not go through any of the pluginA, pluinB etc etc _inner_packages like plugin_a_inner_package_1. With Java Reflections, I'll wind up going through everything in the plugins_package.

Reflections reflections = new Reflections("my_app_package.plugins_package");

 Set<Class<? extends Object>> allClasses =  reflections.getSubTypesOf(Object.class);  

I would only like to go through the root package of a plugin package, say plugins_package.plugin_A then walk out with the the **Start class**, then repeat this for all other plugin packages like plugin_B, plugin_C, etc, etc.