Reflection utils for Java

ReflectionUtils.java

import javax.annotation.Nonnull;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;

public class ReflectionUtils {
    
    private ReflectionUtils() {
    }


    /**
     * Scans all classes accessible from the context class loader which belong to the given package and subpackages. <br />
     * <a href="https://dzone.com/articles/get-all-classes-within-package">Source</a>, with changes to welcome generic system since Java 5.
     * 
     * @param packageName The base package
     * @return The classes
     * @throws ClassNotFoundException
     * @throws IOException
     */
    @Nonnull
    public static List<Class<?>> getClasses(String packageName) throws ClassNotFoundException, IOException {
        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        if (classLoader == null) {
            return new ArrayList<>();
        }
        
        String path = packageName.replace('.', '/');
        Enumeration<URL> resources = classLoader.getResources(path);
        List<File> dirs = new ArrayList<>();
        
        while (resources.hasMoreElements()) {
            URL resource = resources.nextElement();
            dirs.add(new File(resource.getFile()));
        }
        
        List<Class<?>> classes = new ArrayList<>();
        for (File directory : dirs) {
            classes.addAll(findClasses(directory, packageName));
        }

        return classes;
    }
    
    /**
     * Recursive method used to find all classes in a given directory and subdir's. <br />
     * <a href="https://dzone.com/articles/get-all-classes-within-package">Source</a>, with changes to welcome generic system since Java 5.
     *
     * @param directory   The base directory
     * @param packageName The package name for classes found inside the base directory
     * @return The classes
     * @throws ClassNotFoundException
     */
    @Nonnull
    private static List<Class<?>> findClasses(File directory, String packageName) throws ClassNotFoundException {
        List<Class<?>> classes = new ArrayList<>();
        if (!directory.exists()) {
            return classes;
        }
        
        File[] files = directory.listFiles();
        if (files == null) {
            return classes;
        }
        
        for (File file : files) {
            if (file.isDirectory()) {
                if (!file.getName().contains(".")) {
                    return classes;
                }

                classes.addAll(findClasses(file, packageName + "." + file.getName()));
            } else if (file.getName().endsWith(".class")) {
                classes.add(Class.forName(packageName + '.' + file.getName().substring(0, file.getName().length() - 6)));
            }
        }

        return classes;
    }
    
}