java.net.URISyntaxException: Illegal character

最近有個需求
需要將字串轉成JSON
再轉成urlencode
再轉base64
再當成參數去call httpget method
轉好base64之後 我發現在new HttpGet時 就會出exception
ex. java.net.URISyntaxException: Illegal character
應該是字串裡有不合法的字元
後來我用URL跳過去

URL url = new URL(urlstr);
URI uri = new URI(url.getProtocol(), url.getHost(), url.getPath(), url.getQuery(), null);
HttpGet httpget = new HttpGet(uri);