And there is also Codename One which doesn't require a Mac (since we host them in the cloud).
For completeness sake libGDX uses RoboVM which is the actual underlying compiler. There are also XMLVM, J2ObjC & Avian.
Developer Advocate at Lightrun. Co-Founder of Codename One. Java Rockstar, Speaker, Author, Blogger and open source hacker
Of course you can... is not as straight forward as on MacOS where you have your JVM.. legal issues (no technical) have done "impossible" to run a JVM in the iOS environment so you have to "convert you jar packages and distribution in "native iOS programs", i recommed you to take a look to the JavaFX port site: http://javafxports.org/page/home have a nice coding.
In my humble opinion, as long as there is no official support of a Java VM on iOS, any workaround and effort of running java on such platform won't go very far.. with all my respect to solutions like robovm and similar approaches.