How to change java version within a bash script?

Question

I have one piece of a script that needs a different java version to the rest of the script, up till now I've always manually changed versions with sudo update-alternatives --config java and then just select the one I need.

Is there a way to do that within a bash script?

I've tried export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/bin/java which matches the path listed by sudo update-alternatives --config java but if I then type at the command line java -version it still lists the previous java version, and not java-11-openjdk-amd64.

Any help is appreciated.

• GhostCat: What do you mean "when I type"? When you invoke a bash script that does some export, then the "parent" shell that you used to run the script won't see that export? Thus: please see minimal reproducible example and add the relevant part of your code, instead of explaining what your code does.
• user1934428: When you type java, the value of JAVA_HOME is irrelevant. As with every command, the shell searches the PATH variable to located the executable. You can do a type -a java to see all the Java versions in your PATH, in search order.
• Joachim Sauer: Strongly related to this. JAVA_HOME is quite misunderstood and not nearly as important as most people think.

Answer 1

It depends on the tool used, but for most tools PATH is more important than JAVA_HOME.

Here is a script that changes the path and also restores it

#!/bin/bash
original_path=$PATH
java -version
export PATH=/usr/lib/jvm/java-11-openjdk-amd64/bin/:$PATH
java -version
export PATH=$original_path
java -version

If you directly need to invoke a specific java version a single time in your script then you could also do

PATH=/usr/lib/jvm/java-11-openjdk-amd64/bin/:$PATH java -version

Answer 2

The commands jdk8, jdk11 or jdk17

will change the version of java in git bash depending on what version you have installed.

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