public void TryFinderClass(String str, String matchKey) { // String jsonText = "{\"first\": 123, \"second\": [{\"k1\":{\"id\":\"id1\"}}, 4, 5, 6, {\"id\": // 123}], \"third\": 789, \"id\": null}"; String jsonText = str; JSONParser parser = new JSONParser(); KeyFinder finder = new KeyFinder(); // finder.setMatchKey("id"); finder.setMatchKey(matchKey); try { while (!finder.isEnd()) { parser.parse(jsonText, finder, true); if (finder.isFound()) { finder.setFound(false); System.out.println(matchKey + " found:"); System.out.println(finder.getValue()); } } } catch (ParseException pe) { System.out.println(pe.getMessage()); } }