jsonObject.getString() 和jsonObject.optString()区别

//optJSONObject源码解析：
     /**
     * Returns the value mapped by {@code name} if it exists and is a {@code
     * JSONObject}. Returns null otherwise.
     */
    public JSONObject optJSONObject(String name) {
        Object object = opt(name);
        return object instanceof JSONObject ? (JSONObject) object : null ;
    }
    //当返回值不是JSONObject对象时，返回值为null，不抛出异常;


//getJSONObject源码解析：
     /**
     * Returns the value mapped by {@code name} if it exists and is a {@code
     * JSONObject}.
     * @throws JSONException if the mapping doesn't exist or is not a {@code
     * JSONObject}.
     */
    public JSONObject getJSONObject(String name) throws JSONException {
        Object object = get(name);
        if (object instanceof JSONObject) {
            return (JSONObject) object;
        } else {
            throw JSON.typeMismatch(name, object, "JSONObject" );
        }
    }
    //当返回值不是JSONObject对象时，抛出异常;