[[!meta title="Java Micro Edition"]]

Many cell phones and similar devices run a constrained version of the
Java Virtual Machine (JVM) called the Sun Java Wireless Toolkit CLDC ,
Java 2 Micro Edition, or something similar (Sun/Oracle seem to like
changing package names).  If you want to write a MIDlet that runs on
your phone, take a look at Vikram Goyal's detailed [tutorial][VG]
(note: Windows-based commands, but they translate easily into Linux
equivalents).

After installing a J2ME SDK (see below) I worked through the examples
in Vikram's tutorial and those in a [post by Hexist][Hexist], to
compile a simple app.  Here's the source for the app with a cleaned up
`Makefile`:

* [[Makefile]]
* [[HelloWorld.java]]
* [[Manifest]]
* [[!ltio icon.png]]

It's a bit annoying getting a J2ME SDK set up on Linux, because the
[Java Wireless Toolkit][WTK] requires the old and buggy Java 1.5.  On
my Gentoo box, I had to mask version of the JDK greater than 1.5 by
creating `/etc/portage/package.mask/java_wtk` containing the line
    
		>=virtual/jdk-1.6

The Gentoo Portage tree no longer carries Java 1.5 ebuilds, so I
installed the Java overlay

    # layman -a java-overlay

I then started trying to emerge the JDK with calls to

    # emerge -av virtual/jdk

In order for that to succeed I had to:

* Create `/etc/portage/package.keywords/java_wtk` containing
  `dev-java/sun-jdk ~x86` to unmask the JDK.
* Create `/etc/portage/package.use/java_wtk` containing
	`dev-java/sun-jdk -doc` to avoid a fetch restriction on the
	documentation.
* Add `ACCEPT_LICENSE="dlj-1.1"` to `/etc/make.conf` to accept
	Sun's license for Java 1.5.

Take a look at the [Gentoo Java Guide][GJG] page for general
information on running Java on Gentoo.

Once I got the JDK installed, I installed the [Wireless Toolkit][WTK]
in `~/lib/WTK2.5.2` using

    $ equery files sun-jdk | grep /bin/javac

to identify `/opt/sun-jdk-1.5.0.22/` as the Java SDK path.

Anyhow, after getting all that setup, I learned that my
[Verizon-provided Casio C721][C721] is running the ancient [BREW][] OS
3.x (Chris Wright's [history of mobile games][history] says that BREW
went commercial in 2002, but doesn't list specific version release
dates).  To top that off, they charge [$400 for a developer
signature][sig] needed to install apps on *your own phone*.

There is an outside chance that they are getting their act together
though, with vague press releases about [upgrading][] to [Brew MP][]
and [lowering the barrier to entry for app-delivery][open].  I'm
skeptical, but I suppose time will tell.

[VG]: http://today.java.net/pub/a/today/2005/02/09/j2me1.html
[Hexist]: http://hexist.com/?p=29
[GJG]: http://www.gentoo.org/doc/en/java.xml
[WTK]: http://www.oracle.com/technetwork/java/download-135801.html
[C721]: http://developer.verizon.com/jsps/devCenters/DeviceDB/Landing_Pages/BewCasioExilim.jsp
[BREW]: http://en.wikipedia.org/wiki/Binary_Runtime_Environment_for_Wireless
[history]: http://www.pocketgamer.biz/r/PG.Biz/A+Brief+History+of+Mobile+Games/feature.asp?c=10618
[sig]: http://en.wikipedia.org/wiki/Binary_Runtime_Environment_for_Wireless#Development_fees
[upgrading]: http://www.brewmp.com/showcase/verizon-wireless
[Brew MP]: http://www.brewmp.com/
[open]: http://news.vzw.com/news/2010/07/pr2010-06-29.html
[WAP]: http://en.wikipedia.org/wiki/Wireless_Application_Protocol

[[!tag tags/java]]
[[!tag tags/linux]]
[[!tag tags/programming]]