PrettyJson en java sin librerias externas

 private static String prettyJson(String responseBody) throws ScriptException {  
     ScriptEngineManager manager = new ScriptEngineManager();  
     ScriptEngine scriptEngine = manager.getEngineByName("JavaScript");  
     scriptEngine.put("jsonString", responseBody);  
     scriptEngine.eval("result = JSON.stringify(JSON.parse(jsonString), null, 2)");  
     return (String) scriptEngine.get("result");  
   }