Switch java version on linux

Switch between multiple java versions

While installing Android Studio on Ubuntu 14.04 I get the message that my Java version ( javac 1.7.0_79 ) is causing problems. I found a solution of how to install a newer Oracle version of Java:

sudo apt-add-repository ppa:webupd8team/java sudo apt-get update sudo apt-get install oracle-java8-installer 

However I’m afraid that this might overwrite my existing open-jdk version of Java. Since I don’t know which of my programs depend on Java, I fear that this could crash these other programs. Is there a way to make sure apt-get doesn’t overwrite my previous Java? I would basically like to have installed both and be able to switch between them manually, depending on what version I need.

6 Answers 6

Apt-get won’t overwrite the existing java versions.

To switch between installed java versions, use the update-java-alternatives command.

update-java-alternatives --list 

Set java version as default (needs root permissions):

sudo update-java-alternatives --set /path/to/java/version 

. where /path/to/java/version is one of those listed by the previous command (e.g. /usr/lib/jvm/java-7-openjdk-amd64 ).

update-java-alternatives is a convenience tool that uses Debian’s alternatives system ( update-alternatives ) to set a bunch of links to the specified java version (e.g. java , javac , . ).

tq this solve my problem too. @Nenotlep what I did is edit the environment variable manually either in .bashrc or /etc/environment

@Nenotlep in order to change JAVA_HOME you have to run the following command: source /etc/environment

@janb I honestly don’t understand why this would have any effect unless you manually specified JAVA_HOME in /etc/environment . I just switched back and forth between java 8 and 11, and there is still no JAVA_HOME in /etc/environment . In fact, it is set nowhere in my environment. I therefor rejected the suggested edit. If there are circumstances in which the suggested command is needed, please suggest a new edit and explain when and why it would be necessary.

My $JAVA_HOME is unaffected by any of the proposed commands, too. My ~/.bashrc has a line export JAVA_HOME=$(readlink -f /usr/bin/javac | sed «s:bin/javac::») though and that does the trick for me: source ~/.bashrc . If your ~/.bashrc doesn’t have that line, run directly export JAVA_HOME=$(readlink -f /usr/bin/javac | sed «s:bin/javac::») .

sudo update-alternatives --config java 

which lists all installed versions with current active one marked and provides dialog to switch:

There are 3 choices for the alternative java (providing /usr/bin/java). Selection Path. ------------------------------------------------------------ 0 /usr/lib/jvm/java-9-oracle/bin/java. * 1 /usr/lib/jvm/java-7-oracle/jre/bin/java. 2 /usr/lib/jvm/java-8-oracle/jre/bin/java. 3 /usr/lib/jvm/java-9-oracle/bin/java. Press to keep. [*], or type selection number: 

export JAVA_HOME="$(jrunscript -e 'java.lang.System.out.println(java.lang.System.getProperty("java.home"));')" 

to set $JAVA_HOME from current active version

As noted by @danzel at the accepted answer, this affects only the java executable, not the other parts of the configuration. Use update-java-alternatives if available.

Configuring Java

You can configure which version is the default for use in the command line by using update-alternatives , which manages which symbolic links are used for different commands.

sudo update-alternatives --config java 

The output will look something like the following.

There are 5 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ * 0 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 1081 auto mode 1 /usr/lib/jvm/java-6-oracle/jre/bin/java 1 manual mode 2 /usr/lib/jvm/java-7-oracle/jre/bin/java 2 manual mode 3 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 1081 manual mode 4 /usr/lib/jvm/java-8-oracle/jre/bin/java 3 manual mode 5 /usr/lib/jvm/java-9-oracle/bin/java 4 manual mode Press to keep the current choice[*], or type selection number: 

You can now choose the number to use as a default. This can also be done for other Java commands, such as the compiler ( javac ), the documentation generator ( javadoc ), the JAR signing tool ( jarsigner ), and more. You can use the following command, filling in the command you want to customize.

sudo update-alternatives --config command

Setting the JAVA_HOME Environment Variable

Many programs, such as Java servers, use the JAVA_HOME environment variable to determine the Java installation location.

Copy the path from your preferred installation and then open /etc/environment using Sublime Text or your favourite text editor.

At the end of this file, add the following line, making sure to replace the highlighted path with your own copied path.

JAVA_HOME="/usr/lib/jvm/java-8-oracle" 

Save and exit the file, and reload it: source /etc/environment .
You can now test whether the environment variable has been set by executing the following command: echo $JAVA_HOME . This will return the path you just set.

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Techgalery.com

Java is a programming language that has been around for over 20 years and it is still widely used in the development of enterprise software running millions of businesses and organizations all around the universe.

If you want to install a different Java version on Ubuntu OS you can use the simple apt install command like this, first, you can find the Java version you want:

sudo apt search openjdk

And then install the package which JDK version you want that is listed on the list for example I want to install the 11th version like this:

sudo apt-get install openjdk-11-jdk

How To Switch Java Version

You can have multiple Java in your virtual machine, Ubuntu, or any other Linux operating system. And then if you want, you can then switch your Java version using the following Linux command.

sudo update-alternatives —config java

After that, it shows you the existing Java in your OS, if you have multiple of it, you answer the prompt by selecting the Index number on the Java version you want to use globally on your OS.

If you only have one version the command will show you a notice telling you Nothing to configure.

I am an experiences web developer, have a good problem-solving and deep understanding of software development principles. With comprehensive skill set in Java, PHP, Python, C and JavaScript. Able to do database thing like MySQL and Oracle. Along with expertise in frameworks like Spring, React, and Firebase. Have a solid understanding of software development methodologies, like Agile and Scrum. I applies best practices to ensure the development process is efficient and of the highest quality output.

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