How to set multiple versions of Java on linux

Question

I have Java 1.6 installed on my Linux box and all users and programs used it. Now, I need to install a program which uses version 1.7. I want to install this version such that everyone else continues to use 1.6, except that new program. What I am thinking is to install new Java and to keep $JAVA_HOME to point to the old Java 1.6. For that particular process, executed by a separate user, I want to set $JAVA_HOME to point to java 1.7

Is this going to work? It will not overwrite the original $JAVA_HOME? Is it sufficient $JAVA_HOME to point to new java for everything to work?

Note: I don't want that the program to be executed under Java 1.7, the program calls a scripts which must run under 1.7. I don't have permissions neither to modify the program, nor those scripts.

Answer 1

You have to worry about more than just $JAVA_HOME; you also need to set $PATH if you are going to call the commands without an absolute path. ie java and not /opt/java/1.7/bin/java.

Now depending on how your script works or how you call java, you have a few options.

Bash Script

Doing it this way means you do not need to add an extra user

#!/bin/bash JAVA_HOME=/opt/java/1.7 PATH=/opt/java/1.7/bin:$PATH ... 

~/.bashrc

If you want to use another user putting this in your .bashrc is an option. export is used so that $JAVA_HOME and $PATH are made into environment variables.

... export JAVA_HOME=/opt/java/1.7 export PATH=/opt/java/1.7/bin:$PATH ... 

eval

You can also set these environment variables on the fly for a single command and its sub commands

eval JAVA_HOME=/opt/java/1.7 PATH=/opt/java/1.7/bin:$PATH java ${ARGS}