There's no supplied GCJ for iOS. While it could be supported last time I looked GCJ had some strange assumptions around the architecture it uses.
Plus this way it's fairly simple to treat your Java as a business logic layer and code the UI in Cocoa/ObjC. Your UI is going to be device specific anyway.
Plus this way it's fairly simple to treat your Java as a business logic layer and code the UI in Cocoa/ObjC. Your UI is going to be device specific anyway.