scan classes in a package, and load them to a list

package-class-scanner.java

import java.io.File;
import java.io.FilenameFilter;
import java.lang.reflect.Modifier;
import java.net.JarURLConnection;
import java.net.URL;
import java.util.*;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class ClassScanner{
   public static <T> List<Class<? extends T>> listPackageClass(String pkgName, Class<T> superClass) {
        List<Class<? extends T>> result = new ArrayList<Class<? extends T>>();

        ClassLoader classLoader = Thread.currentThread().getContextClassLoader();
        try {
            Enumeration<URL> resources = classLoader.getResources(pkgName.replace(".", "/"));
            while (resources.hasMoreElements()) {
                URL resource = resources.nextElement();
                if (resource.getProtocol().equalsIgnoreCase("jar")) {
                    JarURLConnection urlConnection = (JarURLConnection) resource.openConnection();
                    JarFile jarFile = urlConnection.getJarFile();
                    String prefix = urlConnection.getEntryName();
                    Enumeration<JarEntry> entryEnumeration = jarFile.entries();
                    while (entryEnumeration.hasMoreElements()) {
                        JarEntry entry = entryEnumeration.nextElement();
                        if (entry.isDirectory()) continue;
                        if (!entry.getName().startsWith(prefix)) continue;
                        if (entry.getName().endsWith(".class")) {
                            String className = entry.getName().substring(0, entry.getName().length() - 6).replace("/", ".");
                            loadClass(className, result, superClass);
                        }
                    }
                    continue;
                }
                File f = new File(resource.getFile());
                if (!f.isDirectory()) { // should not be file , but a directory 
                   continue;
                }
                String[] files = f.list(new FilenameFilter() {
                    @Override
                    public boolean accept(File file, String s) {
                        return s.endsWith(".class");
                    }
                });
                for (String classFileName : files) {
                    String className = classFileName.substring(0, classFileName.length() - 6);
                    loadClass(pkgName + "." + className, result);
                }
            }
        } catch (Throwable t) {
            t.printStackTrace();
        }
        
        return result;
    }

  private static <T> void loadClass(String className, List<Class<? extends T>> result, Class<T> superClass) {
        try {
            Class c = Class.forName(className);
            if (superClass.isAssignableFrom(c)
                    && !Modifier.isInterface(c.getModifiers())
                    && !Modifier.isAbstract(c.getModifiers())) {
                result.add(c);
            }
        } catch (Throwable t) {
            t.printStackTrace();
        }
    }
}