I like (need) to have several JDKs installed on my system and I use Debian’s alternatives mechanism to switch easily between them. It’s just a clever use of symlinks. A nice aspect of the alternatives system is the possibility to connect “slaves”: links to other files which should be changed when their master changes. Since the JDK is made up of quite a few commands, here is what I use when I add a new version to my system:

sudo update-alternatives --install /usr/bin/java java $1/bin/java 200 \
--slave /usr/bin/jar jar $1/bin/jar \
--slave /usr/bin/jarsigner jarsigner $1/bin/jarsigner \
--slave /usr/bin/javac javac $1/bin/javac \
--slave /usr/bin/javadoc javadoc $1/bin/javadoc \
--slave /usr/bin/javah javah $1/bin/javah \
--slave /usr/bin/javap javap $1/bin/javap \
--slave /usr/bin/javaws javaws $1/bin/javaws

Then I just invoke the following command to select the JDK I want to use:

sudo update-alternatives --config java

I get presented with the following

There are 5 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                            Priority   Status
------------------------------------------------------------
  0            /usr/lib/jvm/ibm-java-x86_64-60/bin/java         200       auto mode
  1            /usr/lib/jvm/ibm-java-x86_64-60/bin/java         200       manual mode
  2            /usr/lib/jvm/ibm-java-x86_64-70/bin/java         200       manual mode
  3            /usr/lib/jvm/java-1.7.0-openjdk-amd64/bin/java   200       manual mode
  4            /usr/lib/jvm/jdk1.6.0_31/bin/java                200       manual mode
* 5            /usr/lib/jvm/jdk1.7.0_03/bin/java                200       manual mode

Press enter to keep the current choice[*], or type selection number:

And when you need to dynamically set JAVA_HOME to the appropriate path, use the following command:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")