Hi Jaych1000
There's a lot of different objects returned by the library. ENDuration is one of them.
getDuration returns an ENDuration object, which contains the duration property.
so as plamere said, you should use :
float duration = track.getDuration().duration;
or
ENDuration d = track.getDuration();
float duration = d.duration.
I'm still working on a better version of the lib, but you can find a lot of infos here :
http://www.melkaone.net/echonestp5/reference/index.html