String str = "abc";
InputStream inputStream = new ByteArrayInputStream(str.getBytes());

String inputStream2String(InputStream is) {
    BufferedReader in = new BufferedReader(new InputStreamReader(is));
    StringBuffer buffer = new StringBuffer();
    String line = "";
    try {
        while ((line = in.readLine()) != null) {
            buffer.append(line);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    return buffer.toString();
}

String result = "abc";

byte[] encodeRes = Base64.decode(result, Base64.DEFAULT);

String res = new String(encodeRes);

Base64.encodeToString(str.getBytes(), Base64.DEFAULT);

jstring jstr;
char str[]="Hello World/n";
jstr=env->NewStringUTF(str);
return jstr;