Debian 7 "Wheezy"
For DebianWheezy and later releases, Sun Java is no longer available in the repositories. However, java-package can be used to generate Debian packages from the upstream distributables of the JDK as provided by Oracle.
To create packages for DebianWheezy and later, do the following.
Download the appropriate JDK from http://www.oracle.com/technetwork/java/javase/downloads/index.html or chose an older version if your needs require you to run an insecure version
Type in the following command:
$ make-jpkg <downloaded_jdk_file>
Note that some software requires the JDK to be installed in a specific location. For example, to build Android Gingerbread or later, JDK 6 must be used, and the Android build system expects JDK 6 to be installed in /usr/lib/jvm/java-6-sun. With the generated package, JDK 6 is installed in /usr/lib/jvm/j2sdk1.6-oracle. Simply create a symlink from /usr/lib/jvm/java-6-sun -> /usr/lib/jvm/j2sdk1.6-oracle. Creating the symlink automatically has been requested at 701782.
More information is available on the JavaPackage page.
Debian 6.0 "Squeeze"
For DebianSqueeze Sun Java is available in non-free. Either install the Java development kit:
# apt-get install sun-java6-jdk
or the Java runtime environment:
# apt-get install sun-java6-jre
sun-java6-plugin could be installed to activate JVM in your Web browser like Iceweasel
Configure the default Java version
Sun recommends you update the alternatives system to have Sun's tools as the default:
# update-java-alternatives -s java-6-sun