Java8 的寫法可以這樣 final Base64.Decoder decoder = Base64.getDecoder(); final Base64.Encoder encoder = Base64.getEncoder(); final String text = "字串文字"; final byte[] textByte = text.getBytes("UTF-8"); //編碼 final String encodedText = encoder.encodeToString(textByte); System.out.println(encodedText); //解碼 System.out.println(new String(decoder.decode(encodedText), "UTF-8")); base64 wiki : https://zh.wikipedia.org/wiki/Base64