HollowObjectMapper mapper = new HollowObjectMapper(writeEngine); mapper.add(new TypeA(1, "one")); mapper.add(new TypeA(2, "two")); mapper.add(new TypeA(3, "three")); mapper.add(new TypeA(1, "one")); mapper.add(new TypeA(2, "two")); mapper.add(new TypeA(3, "four")); mapper.add(new TypeA(2, "two")); mapper.add(new TypeA(3, "four"));