I've got a lot of experience in Java but none developing mobile apps. I'd like to write an application using Java/Swing and then convert it for use on an Android phone.
Is this feasible or do I really need to develop from the ground up for the Android platform?
I don't own an Android phone as I can't afford one at the moment, and the Android emulator is so slow that I find myself wasting a lot of time sitting around waiting.
Alot of the code from Java is the same in Android but I would say don't. Android uses its own UI system and it would be hard to transfer from swing. Also when you get deeper into the Layouts the Android system has the application would be completely screwed up. Not to mention the whole Intent, Receiver, Content Provider aspects would not transfer properly. Then you need to think about memory. Simple answer in my opinion... no.
If you use the control-model-view paradigm so that your application logic is separated from your display logic, then you should be able to port your application logic from ordinary Java to Android with few or no changes. As for the display logic, that will have to be rewritten using the Android SDK.
With Intent/Activities, in many ways Android applications need to be designed like web apps with pages connected by links. It's quite a different paradigm, so until you know it well I would develop straight onto Android.