code: public static PathFilter getInputPathFilter(JobConf conf) {
      Class<? extends PathFilter> filterClass = conf.getClass(
  	"mapred.input.pathFilter.class", null, PathFilter.class);
      return (filterClass != null) ?
          ReflectionUtils.newInstance(filterClass, conf) : null;
    }
docs: Get a PathFilter instance of the filter set for the input paths.
  
  @return the PathFilter instance set for the job, NULL if none has been set.