code: public final void crossValidate(final TrainingParameters params) {
  
      POSTaggerCrossValidator validator = null;
      try {
        validator = getPOSTaggerCrossValidator(params);
        validator.evaluate(this.trainSamples, this.folds);
      } catch (final IOException e) {
        System.err.println("IO error while loading training set!");
        e.printStackTrace();
        System.exit(1);
      } finally {
        try {
          this.trainSamples.close();
        } catch (final IOException e) {
          System.err.println("IO error with the train samples!");
        }
      }
      if (this.detailedListener == null) {
        System.out.println(validator.getWordAccuracy());
      } else {
        // TODO add detailed evaluation here
        System.out.println(validator.getWordAccuracy());
      }
    }
docs: Cross validate when no separate testset is available.
  
  @param params
  the training parameters