I've followed this: <https://dev.twitter.com/docs/auth/creating-signature>

to the end but I can't find how to encode a "binary string" to base64(at the end). I wanted to try online converters first but they don't give the string the show 
"tnnArxj06cWHq44gCs1OSKk/jLY=" 

Tried this: <http://www.motobit.com/util/base64-decoder-encoder.asp>

and 

<http://www.hash-cracker.com/base64.php#anchor>

and 

<http://www.opinionatedgeek.com/dotnet/tools/Base64Encode/>

and none give that string.

I'm going to be using java. But I think all those java tools I search for will give the same result as the online converters. What has to be done to encode a "binary string" to base64?