Build warnings regarding using Sun proprietary API

It's not clear why you're declaring your own HttpURLConnection and Handler classes in the first place - are you sure you want to compile those?

As for Base64 - I like this public domain implementation myself.

If you have written a http client then you've reinvented the wheel. There's a really good one already in apache http client.

If you want Base64 encoding/decoding there's an class for that in apache commons codec.

Apache Commons Codec include Base64 class.