Java JRE/JDK installation

To verify that the installation was successful, execute

java -version

The output should look something like this if everything is well

java version "1.5.0_05"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_05-b05)
Java HotSpot(TM) Client VM (build 1.5.0_05-b05, mixed mode)

If the version does not match what you just installed then you might have JRE/JDK installed previously

Multiple JRE/JDK installed

If you have multiple JRE or JDK installed (e.g. 1.5.0 and 1.4.2) and want/need to switch between them, you can use update-alternatives to do so.

Example: Choosing which java executable to use:

update-alternatives --config java

Example: Choosing which javac executable to use:

update-alternatives --config javac

And so on in that fashion for the remaining executables related to Java. You can look in /etc/alternatives to see what one can configure with update-alternatives.
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