Change java versions linux

How to change the default Java version on Ubuntu

If you are a Java developer, it is normal to have multiple Java versions installed on your machine to support different build environments. When a Java program is compiled, the build environment sets the oldest JRE version the program can support. Now, if you run this program on a Linux machine where an unsupported Java version is installed, you will encounter an exception.

For example, if your program is compiled on Java 11, it can’t be run on a machine where Java 8 is installed. But the good thing is you can install multiple Java versions on your machine and quickly change the default JRE version.

In this tutorial, I’ll explain how to change the default Java version on a Linux machine. First of all, run the following command to check the current Java version:

As you can see above, the default Java version is currently set to OpenJDK JRE 1.8. Now, let’s run the following command to see all available Java versions:

Running the above command displays a list of installed Java JDKs and JREs allowing you to select the one as you want to set as default.

When prompted, select the Java version you would like to use. If the list does not include your desired Java version, you can always install it.

Now you can verify the default Java version as fellows:

That’s it. The default Java version is changed to OpenJDK 11.

Bonus: Use Script to Switch Java Version

If you frequently switch between different Java versions, it is a good idea to write a short script to automate the process. Here is the script I used for switching to OpenJDK 8 on my machine.

Similarly, you can create scripts for other Java versions installed on your machine. The next step is to add these scripts as aliases to .bashrc file.

Next, run the following command to load the changes of .bashrc file:

Now if you want to switch to Java 8, just type the following command in your terminal:

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Switching between Java Versions on Ubuntu linux

If you’re using Ubuntu Linux on your daily basis work, you’ve probably Java installed on your machine. Personally I prefer using Wepupd8 PPA to manage JAVA installation, it makes my life a lot more easier especially for updates. The Wepupd8 team didn’t add any binary for Oracle JAVA installation and they made a script to download the Oracle JAVA from Oracle website and install it straight away. So whenever Oracle will release the update, I can simple upgrade via package manager.

Working with multiple Java versions in your machine is a normal thing, especially if you’re a Java developer, and because I’m a (very) lazy person, I’m always looking for a quicker/easier way to make the switch.

Today, I’ll share with you my tip on this subject. First, let’s run the following command:

$ sudo update-alternatives —config java

Running this command shows a list of installed Java JDKs and JREs allowing one to be selected as the default that is used when java needs to be executed.

But I’m using it just to get the Installation path of each Java version.

Then, for each version I created a script that contain the following lines (in the example below, I’m showing the one for java 8):

Note that I’m using u8.sh to make he switch to Java 8, and u9.sh for Java 9 and so on.
The final step is to add an alias in

/.bashrc file to source our script as follow:

and That’s all. Now for switching between Java versions, I only run u8, u7 or u9 😉

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How to change Default Java /JDK Version and ClassPath in Linux using .bash_profile?

Last Updated on October 4th, 2020 by App Shah 2 comments

When you install Java with default apt install command on Ubuntu or CentOS Linux OS then it will install Java under default folder /usr/bin/java .

First thing first. How to install or upgrade JVM in Linux OS?

Please make sure to upgrade to Latest JDK. Today I installed JDK 15. (Oct 2020)

Use below linux command to install latest Java in Ubuntu, CentOS:

# apt install openjdk-9-jre-headless

As you see above, I already have latest JDK 9 installed and then there is no need to download any extra package here. For new re-imaged host it will completely install new Java/JDK binary for you.

After that – just use command which java to find out CLASSPATH variable. In my case it’s /usr/bin/java .

BEFORE:

This is the default Java version available for you to use. With simple command java -version you will see which JDK it referred to.

This is an ideal situation for most of the cases if you are the only one working on project. But it’s not the case for most of the companies out there 🙂

Usually, in production, companies ship Java with their project binary. During runtime they setup CLASSPATH and PATH respectively to use preferred Java version.

Want to change default JVM version in Ubuntu Linux OS? Or CentOS Linux?

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Future is here!

Future is here!

Change default Java version in Ubuntu 20.04 LTS

We consider this article to be an extension to the previous article – Install OpenJDK JRE / JDK in Ubuntu 20.04 LTS . As you would notice, we have already installed version 11 of OpenJDK JRE / JDK in Ubuntu 20.04 LTS release. Now, consider a scenario wherein we have also installed version 8 of OpenJDK JRE. In that case, the default version would still be the one which we have installed earlier i.e. version 11.0.7. So, in this article we would discuss how to change the default Java version in Ubuntu 20.04 LTS.

Just for clarity, we would first install OpenJDK Development Kit v11.0.7 and OpenJDK Java Runtime Environment v1.0.8_252. Thereafter, we would issue the specific command to change the default version of Java.

Note: Following operations would require you to have superuser privileges. In case you don’t have one, then contact your System Administrator for assistance.

Install different versions of OpenJDK Development Kit and Java Runtime Environment

Since the packages are already available in standard Ubuntu repository. Therefore, first update the Ubuntu repository to make the latest version of the package available. Hence, issue the following in terminal –

Now, to install OpenJDK Development Kit v11.0.7 –

Next, to install OpenJDK Java Runtime Environment v1.8.0_252 –

Change default Java version in Ubuntu 20.04 LTS

First, verify for the Java version installed –

It would return the output –

Although we already installed version 1.8.0_252, But, when we pass the java -version command then it doesn’t mention the said version. Because, as of now v11.0.7 is the default version. To change that, we need to issue command –

It would show us all the Java versions installed. Enter the selection number for OpenJDK JRE v1.8.0_252. Again –

This time it would return with –

In conclusion, we have discussed how to change the default version of Java in Ubuntu 20.04 LTS release.

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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:

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.

List all java versions:

Set java version as default (needs root permissions):

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

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 , . ).

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

to set $JAVA_HOME from current active version

Based on the answer from @muet, I found this to work seamlessly:

Then you can switch within the same shell using only: useJava7 or useJava8

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.

The output will look something like the following.

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.

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.

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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