### Question:
JsonBuilder { public static String writeJsonString(Object o) throws Exception { return DEFAULT.writeValueAsString(o); }  static T readValue(Map<String, Object> jsonMap, Class<T> reference); static T readValue(String jsonString, TypeReference<T> reference); static T readValue(String jsonString, Class<T> reference); static String writeJsonString(Object o);  }### Answer:
@Test public void writeJsonString() throws Exception { TestB b = new TestB(); b.setAge(100); b.setName("testName"); TestInf inf = new TestC(b); assertEquals(JSON, JsonBuilder.writeJsonString(inf)); }