Packages providing a runtime or a development environment for the Java
language all use symlinks in the /etc/alternatives directory to enable
the system administrator to choose which programs to use for java,
javac, javah, etc.

Starting with java-common 0.23ubuntu1, the update-java-alternatives
script can be used to set a bunch of jre/jdk alternatives:

- Set all runtime tools to point to the @basename@ alternatives:

  update-java-alternatives --jre --set java-6-sun


- Set all runtime and development tools to point to the @basename@
  alternatives:

  update-java-alternatives --set java-6-sun


- Set all runtime and development tools to auto mode:

  update-java-alternatives --auto