filter = (FileFilter)Class.forName(filterclass).getConstructor(new Class[] { Configuration.class, String.class }).newInstance(new Object[] {conf, pattern});
if(str.length()!=0){
str.append(FileFilter.SEPARATOR);
}
str.append(filter.filter(new Path(path)));
} catch (IllegalArgumentException e) {
// TODO Auto-generated catch block
e.printStackTrace();