public static String getString(JSONObject json, String key) {
        return getString(json, key, null);
    }
public static String getString ( JSONObject json , String key ) { return getString ( json , key , null ) ; }
Returns the value of a JSON property as a String if it exists otherwise returns null.
Same as calling {@link #getString(net.sf.json.JSONObject, java.lang.String, java.lang.String) }
with null as defaultValue.
@param json the JSONObject to check.
@param key the key.
@return the value for the key as a string.