On the JDK 1.4.2, both sun/misc/BASE64Encoder and sun/misc/
BASE64Decoder come in the standard distribution, on a jarfile called
classes.jar.

However... you should not rely on these classes. See:

http://java.sun.com/products/jdk/faq/faq-sun-packages.html

Maybe other JREs don't include such classes.... ibm? gcj? ..

Try something like apache jakarta commons codec for a ever compatible
implementation for Base64.

Best regards.

See http://mindprod.com/jgloss/base64.html

Using internal Java classes from SUN is not recommended.

Use the supported Base64 in JavaMail.

    public static String b64encode(byte[] b) throws MessagingException,
IOException  {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        OutputStream b64os = MimeUtility.encode(baos, "base64");
        b64os.write(b);
        b64os.close();
        return new String(baos.toByteArray());
     }
     public static byte[] b64decode(String s) throws
MessagingException, IOException  {
        ByteArrayInputStream bais = new ByteArrayInputStream(s.getBytes());
        InputStream b64is = MimeUtility.decode(bais, "Base64");
        byte[] tmp = new byte[s.length()];
        int n = b64is.read(tmp);
        byte[] res = new byte[n];
        System.arraycopy(tmp, 0, res, 0, n);
        return res;
     }

Arne