json数据：

{ 
    "resultcode": "200","reason": "SUCCESSED!","result": [ 
        { 
            "city": "苏州","PM2.5": "73","AQI": "98","quality": "良","PM10": "50","CO": "0.79","NO2": "65","O3": "28","SO2": "41","time": "2014-12-26 11:48:40"
        }
    ],"error_code": 0
}

 JSONObject jsonObject = new JSONObject(result);  
          int resultCode = jsonObject.getInt("resultcode");  
          if (resultCode == 200) {  
              JSONArray resultJsonArray = jsonObject.getJSONArray("result");  
              JSONObject resultJsonObject = resultJsonArray.getJSONObject(0);//如果是用第一个对象就如下所写的，如果是数组就用循环，在新建一对象resultJsonObject
              String output =  resultJsonObject.getString("city"); 
                      resultJsonObject.getString("PM2.5") ;
                      resultJsonObject.getString("AQI");
                      resultJsonObject.getString("quality"); 
                       resultJsonObject.getString("PM10"); 
                      resultJsonObject.getString("CO") ; 
                      resultJsonObject.getString("NO2") ; 
                      resultJsonObject.getString("O3") ; 
                      resultJsonObject.getString("SO2") ; 
                     resultJsonObject.getString("time"); 
          }

json数据：

  {
        "crset":[
            {
                "merchantname":"三火餐厅","menu":[
                    {
                        "menuid":"1","menuname":"酸菜鱼"
                    },{
                        "menuid":"2","menuname":"麻婆豆腐"
                    },{
                        "menuid":"3","menuname":"酸菜鱼"
                    }
                ]
            },{
                "merchantname":"粤菜餐厅","menuname":"炒生菜"
                    },"menuname":"蒸鱼"
                    },"menuname":"煎豆腐"
                    }
                ]
            },{
                "merchantname":"西式餐厅","menuname":"牛扒"
                    },"menuname":"罗宋汤"
                    },"menuname":"三文治"
                    }
                ]
            }
        ]
    }

public class Merchants {
	private List<Merchant> merchant;
}

public class Merchant{
	private String merchantname;
	private List<Menu> menu;
}

public class Menu {
	private String menuid;

	private String menuname;

}

解析数据如下

JSONObject jsonObject = new JSONObject(json);// json上方返回的数据
	JSONArray jsonArray =jsonObject.getJSONArray("crset");
	List<Merchant> merchants = new ArrayList<Merchant>();
	for(int i = 0;i<jsonArray.length();i++)
	{
		// 解析每个merchant
		JSONObject item = jsonArray.getJSONObject(i);
		Merchant merchant = new Merchant();
		merchant.setMerchantname(item.getString("merchantname"));
		// 解析每个menu
		List<Menu> menus = new ArrayList<Menu>();
		JSONArray array = item.getJSONArray("menu");
		for (int j = 0; j < array.length(); j++) {
			JSONObject menuitem = array.getJSONObject(i);
			Menu menu = new Menu();
			menu.setMenuid(menuitem.getString("menuid"));
			menu.setMenuname(menuitem.getString("menuname"));
			menus.add(menu);
		}
		merchant.setMenu(menus);
		merchants.add(merchant);
	}