presto-main/src/main/java/io/prestosql/server/PluginDiscovery.java/PluginDiscovery/visitFile
class PluginDiscovery:    private static List<String> listClasses(Path base)
            throws IOException
    {
        ImmutableList.Builder<String> list = ImmutableList.builder();
        walkFileTree(base, new SimpleFileVisitor<Path>()
        {
            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attributes)
            {
                if (file.getFileName().toString().endsWith(CLASS_FILE_SUFFIX)) {
                    String name = file.subpath(base.getNameCount(), file.getNameCount()).toString();
                    list.add(javaName(name.substring(0, name.length() - CLASS_FILE_SUFFIX.length())));
                }
                return FileVisitResult.CONTINUE;
            }
        });
        return list.build();
    }