Java Phone Apps on Android
Java was designed so that it should run on all phones. The founder of Apple computers who invented the iPhone rejected Java and said it was a slow and dead technology. He provided no support for Java on the iPhone and would not accept apps that run on a virtual machine in the Applet app Store. As a result, no one, as far as I know, has made a virtual machine for the iPhone or iPad. No phones would support Java if it were not for Google. Google has made a version of Linux which is Android OS and made up special Java API for Android. By the way, Google makes heavy use of Java technology within its systems. Google even hired one of the main Java guru's away from Sun.
Java on other Phones
Java will run on a few brands of phones other than the Android I assume with some setup required. Java apps will also run on some tablets and specifically Android tablets. Java had a micro edition at one time for just such ventures, but at the time was for Personal Data Assistants (PDA) such as Palm Pilot. Those have lost popularity and died as a result of tablets and smartphones. I'm not sure at this time if Java ME is used for phone and tablet development or not.
That's about all I know for now. Come back later and hopefully I will update this article with more information on this.