I was attending the session presented by Mark Reinhold about the modular Java platform and Jigsaw. Mark already gave a preview of the modularity of open JDK7 on ubuntu during the general session on day 1.

Mark already talked about why the JDK had to become a modular JDK. When Java started the JDK contained only a few core packages and classes but during the years the JDK has accumulated more and more core api classes. For embedded devices this is a problem. Also some classes internally in the core api had to many dependencies all over that some sort of modularization was in order. Mark gave the example of loading a temp file to illustrate that.

JSR 294 and for humans Improved Modularity Support in the JavaTM Programming Language is the spec on how the modularization will be done.

So a little example on how the modularized dependency will look like (probably):

module org.domain@1.0{
  requires jdom@1.0
  requires xpath@1.0
  //etc
}

With this code the classpath will also be history with the java modular system. Mark was quite clear about that

Further more Mark showed us a nice demo of the packaging and distribution of Java apps on ubuntu. De JDK modules will be normal debian packages and you will be able to create your own Java application, export it to a debian package and define a dependency towards the java modules you need to run your app. Quite nice.

If you want to read up to everything around Java7 check out the blogrol Alex Miller set up here.