Ubuntu uses OpenJDK by default, but I note that some web services such as ezyZip.com might need the Sun Java Runtime Environment (JRE) to be installed in the system for running the services properly. If you would like to get the proprietary Sun Java packages for your system, you can download and install them from the Canonical Partner Repository with the steps below:
1. Go to Applications (or Main Menu) > Accessories > Terminal.
sudo add-apt-repository "deb http://archive.canonical.com/ lucid partner"
to add the partner repository.
sudo apt-get update
to update the source list.
sudo apt-get install sun-java6-jre sun-java6-plugin sun-java6-fonts
to download and install the Sun Java packages. (If asked to accept the Distributor License for Java (DLJ) terms, use the left/right key to navigate and select Yes, then press the Enter key for installation).
sudo java -version
to check the version of the Java used in the system.
sudo update-alternatives --config java
to choose the default Java for use in the system when necessary.