#vulnerable code 
                             @Test
	public void toJsonStrTest2() {
		Map<String, Object> model = new HashMap<String, Object>();
		model.put("mobile", "17610836523");
		model.put("type", 1);

		Map<String, Object> data = new HashMap<String, Object>();
		data.put("model", model);
		data.put("model2", model);

		JSONObject jsonObject = JSONUtil.parseObj(data);

		Assert.assertTrue(jsonObject.containsKey("model"));
		Assert.assertEquals(1, jsonObject.getJSONObject("model").getInt("type").intValue());
		Assert.assertEquals("17610836523", jsonObject.getJSONObject("model").getStr("mobile"));
		// Assert.assertEquals("{\"model\":{\"type\":1,\"mobile\":\"17610836523\"}}", jsonObject.toString());
	} 
                            #location 14 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                             @Test
	public void toJsonStrTest2() {
		Map<String, Object> model = new HashMap<>();
		model.put("mobile", "17610836523");
		model.put("type", 1);

		Map<String, Object> data = new HashMap<>();
		data.put("model", model);
		data.put("model2", model);

		JSONObject jsonObject = JSONUtil.parseObj(data);

		Assert.assertTrue(jsonObject.containsKey("model"));
		Assert.assertEquals(1, jsonObject.getJSONObject("model").getInt("type").intValue());
		Assert.assertEquals("17610836523", jsonObject.getJSONObject("model").getStr("mobile"));
		// Assert.assertEquals("{\"model\":{\"type\":1,\"mobile\":\"17610836523\"}}", jsonObject.toString());
	}