What do I set as JAVA_HOME?

Question

I just installed Ubuntu desktop 12.04 and installled Java 6 JDK via:

sudo apt-get install openjdk-6-jre

When I issue a `java -version command, I get:

OpenJDK Runtime Environment (IcedTea6 1.11.3) (6b24-1.11.3-1ubuntu0.12.04.1) OpenJDK 64-Bit Server VM (build 20.0-b12, mixed mode)

When I issue a 'which java` command, I get:

/usr/bin/java

But when I go to /usr/bin/, I don't see a directory named java, so I don't think it's even there!?!

When I go to /usr/lib/jvm/, I see:

-rw-r--r--   1 root root  2387 Jun 27 05:21 .java-1.6.0-openjdk-amd64.jinfo
drwxr-xr-x   5 root root  4096 Aug 31 19:28 java-6-openjdk-amd64
drwxr-xr-x   3 root root  4096 Aug 31 19:28 java-6-openjdk-common
drwxr-xr-x   5 root root  4096 Aug 31 19:28 java-7-openjdk-amd64

I'm now trying to add JAVA_HOME as an environmental variable to ~/.bashrc so I can access it from inside my shell-based Ant builds:

export JAVA_HOME=???

I'm not sure what to set as the value for JAVA_HOME:

• /usr/bin/java?
• /usr/lib/jvm?
• Something else?

By "JAVA_HOME", I mean the top-level directory of the JDK 6 install that I have on my system, wherever that is...

Answer 1

I don't have $JAVA_HOME configured on my Linux box - and I don't recall a time ever needing to do so.

When you're looking in /usr/bin, you're looking at binaries - hence bin. A quick look at what the file is would reveal that it's a symbolic link, which points a symbolic link which points to wherever your Java installation resides.

$ file `which java`
/usr/bin/java: symbolic link to `/etc/alternatives/java'

It is a better choice to let the system configure it for you - either through the use of update-alternatives or update-java-alternatives - the latter being preferred to switch over entire versions of Java entirely.

Answer 2

Let the system configure it for you

sudo update-alternatives --config java

For further reference, see Choosing the default Java to use of the Ubuntu documentation.