ConnectionSnippet.java

URL requestUrl = new URL(fullURLRequest);
HttpUrlConnection urlConnection = (HttpURLConnection) requestUrl.openConnection();
InputStream inputStream = new BufferedInputStream(urlConnection.getInputStream());
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
StringBuilder jsonString = new StringBuilder();
// You only want to call readLine once - the assignment will fail once readLine is null;
// calling ReadLine twice will cause an error.
while (String line = bufferedReader.readLine()) {
  jsonString.append(line);
}

JSONObject obj = new JSONObject(jsonString);
WeatherUnderGroundData weatherData = new WeatherUnderGroundData();
weatherData.fromJson(obj);

weather_underground.json

{
  "response": {
    "version": "0.1",
    "termsofService": "http://www.wunderground.com/weather/api/d/terms.html",
    "features": {
      "conditions": 1,
      "astronomy": 1
    }
  },
  "current_observation": {
    "image": {
      "url": "http://icons.wxug.com/graphics/wu2/logo_130x80.png",
      "title": "Weather Underground",
      "link": "http://www.wunderground.com"
    },
    "display_location": {
      "full": "Oakland, CA",
      "city": "Oakland",
      "state": "CA",
      "state_name": "California",
      "country": "US",
      "country_iso3166": "US",
      "zip": "94609",
      "magic": "1",
      "wmo": "99999",
      "latitude": "37.830000",
      "longitude": "-122.270000",
      "elevation": "31.00000000"
    },
    "observation_location": {
      "full": "Longfellow, Oakland, California",
      "city": "Longfellow, Oakland",
      "state": "California",
      "country": "US",
      "country_iso3166": "US",
      "latitude": "37.832680",
      "longitude": "-122.274101",
      "elevation": "63 ft"
    },
    "estimated": {},
    "station_id": "KCAOAKLA43",
    "observation_time": "Last Updated on February 22, 9:22 PM PST",
    "observation_time_rfc822": "Mon, 22 Feb 2016 21:22:26 -0800",
    "observation_epoch": "1456204946",
    "local_time_rfc822": "Mon, 22 Feb 2016 21:22:31 -0800",
    "local_epoch": "1456204951",
    "local_tz_short": "PST",
    "local_tz_long": "America/Los_Angeles",
    "local_tz_offset": "-0800",
    "weather": "Mostly Cloudy",
    "temperature_string": "51.7 F (10.9 C)",
    "temp_f": 51.7,
    "temp_c": 10.9,
    "relative_humidity": "94%",
    "wind_string": "Calm",
    "wind_dir": "NNE",
    "wind_degrees": 22,
    "wind_mph": 0,
    "wind_gust_mph": 0,
    "wind_kph": 0,
    "wind_gust_kph": 0,
    "pressure_mb": "1020",
    "pressure_in": "30.12",
    "pressure_trend": "0",
    "dewpoint_string": "50 F (10 C)",
    "dewpoint_f": 50,
    "dewpoint_c": 10,
    "heat_index_string": "NA",
    "heat_index_f": "NA",
    "heat_index_c": "NA",
    "windchill_string": "NA",
    "windchill_f": "NA",
    "windchill_c": "NA",
    "feelslike_string": "51.7 F (10.9 C)",
    "feelslike_f": "51.7",
    "feelslike_c": "10.9",
    "visibility_mi": "10.0",
    "visibility_km": "16.1",
    "solarradiation": "--",
    "UV": "0",
    "precip_1hr_string": "0.00 in ( 0 mm)",
    "precip_1hr_in": "0.00",
    "precip_1hr_metric": " 0",
    "precip_today_string": "0.00 in (0 mm)",
    "precip_today_in": "0.00",
    "precip_today_metric": "0",
    "icon": "mostlycloudy",
    "icon_url": "http://icons.wxug.com/i/c/k/nt_mostlycloudy.gif",
    "forecast_url": "http://www.wunderground.com/US/CA/Oakland.html",
    "history_url": "http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCAOAKLA43",
    "ob_url": "http://www.wunderground.com/cgi-bin/findweather/getForecast?query=37.832680,-122.274101",
    "nowcast": ""
  },
  "moon_phase": {
    "percentIlluminated": "100",
    "ageOfMoon": "15",
    "phaseofMoon": "Full",
    "hemisphere": "North",
    "current_time": {
      "hour": "21",
      "minute": "22"
    },
    "sunrise": {
      "hour": "6",
      "minute": "50"
    },
    "sunset": {
      "hour": "17",
      "minute": "55"
    },
    "moonrise": {
      "hour": "18",
      "minute": "11"
    },
    "moonset": {
      "hour": "6",
      "minute": "41"
    }
  },
  "sun_phase": {
    "sunrise": {
      "hour": "6",
      "minute": "50"
    },
    "sunset": {
      "hour": "17",
      "minute": "55"
    }
  }
}

WeatherUnderGroundData.java

public class WeatherUnderGroundData {
  private String weatherType;
  private String temp_f;
  private String temp_c;
  private String wind_mph;
  private String wind_kph;
  private String display_location;
  
  private String sunriseHour;
  private String sunriseMinute;
  private String percentIlluminated;
  
  public WeatherUnderGroundData() {
    
  }
  
  public void fromJson(JSONObject obj) {
    this.weatherType = obj.current_observation.weather;
    this.temp_f = obj.current_observation.temp_f;
    this.temp_c = obj.current_observation.temp_c;
    // etc
  }
}

For ConnectionSnippet.java:
String line = bufferedReader.readLine();
while (line != null ) {
jsonString.append(line);
line = bufferedReader.readLine();
}