### Question:
FeatureRenamer extends AbstractDatasetFeatureVectorTransformer { public FeatureRenamer(Function<String, String> featureNameMapping) { Validate.notNull(featureNameMapping, "featureNameMapping must not be null"); this.featureNameMapping = featureNameMapping; } FeatureRenamer(Function<String, String> featureNameMapping);  FeatureRenamer(String regex, String replacement); @Override FeatureInformation getFeatureInformation(FeatureInformation featureInformation); @Override FeatureVector apply(FeatureVector featureVector);  }### Answer:
@Test public void testFeatureRenamer() { Instance instance = new InstanceBuilder().set("a", 1).set("b", 2).create(true); Dataset dataset = new DefaultDataset(Arrays.asList(instance)); dataset = dataset.transform(new FeatureRenamer("^.*$", "renamed_$0")); Instance transformedInstance = dataset.iterator().next(); Iterator<VectorEntry<String, Value>> iterator = transformedInstance.getVector().iterator(); assertEquals(1, ((NumericValue) iterator.next().value()).getInt()); assertEquals(2, ((NumericValue) iterator.next().value()).getInt()); assertEquals(1, transformedInstance.getVector().getNumeric("renamed_a").getInt()); assertEquals(2, transformedInstance.getVector().getNumeric("renamed_b").getInt()); }