### Question:
CategoricalFeature implements Feature { @Override public String toString() { return ":" + encoding; } private  CategoricalFeature(int encoding); static CategoricalFeature forEncoding(int encoding); int getEncoding(); @Override FeatureType getFeatureType(); @Override String toString(); @Override int hashCode(); @Override boolean equals(Object o);  }### Answer:
@Test public void testToString() { CategoricalFeature f = CategoricalFeature.forEncoding(1); assertEquals(":1", f.toString()); }