### Question:
ParameterizableStringListFactory extends AbstractFeatureFactory<T> { @Override public List<T> permute(int maxSize) { Set<T> collector = new HashSet<>(); T currFeatures = (T)newInstance(Collections.EMPTY_LIST); for (int i = 0; i < factories.size(); i++) { recurse(i, maxSize, currFeatures, collector); } return new ArrayList<>(collector); } ParameterizableStringListFactory(String name, Class clazz,
                                            List<ParameterizableStringFactory> factories,
                                            int minSetSize, int maxSetSize); @Override T random(); @Override List<T> permute(int maxSize); @Override T mutate(ParameterizableStringListFeature listFeature,
                                                   double probability, double amplitude); @Override Pair<T, T> crossover(T parentA, T parentB);  }### Answer:
@Test public void testPermute() { String paramString1 = "abc[1,2,3],[4,5,6],[$2])"; String paramString2 = "def[7,8,9],[10,11,12],[$2])"; String paramString3 = "ghi[13,14,15],[16,17,18],[$2])"; List<ParameterizableStringFactory> factories = new ArrayList<>(); factories.add(new ParameterizableStringFactory("bf", "0", TestParam.class, paramString1)); factories.add(new ParameterizableStringFactory("bf", "0", TestParam.class, paramString2)); factories.add(new ParameterizableStringFactory("bf", "0", TestParam.class, paramString3)); ParameterizableStringListFactory parameterizableStringListFactory = new ParameterizableStringListFactory( "name", TestParamList.class, factories, 1, 3); List<ParameterizableStringListFeature> features = parameterizableStringListFactory.permute(10000); List<String> strings = new ArrayList<>(); assertEquals(918, features.size()); }