How To Install And Switch Between Alternative Java Versions

image from

Java is a general purpose computer programming language. Sometimes you have to work with different versions of java at the same time. In such cases you have to switch between versions.

First lets see how to install java on your Ubuntu machine.

Step 1

Check whether your Ubuntu is 32-bit or 64-bit

file /sbin/init

Or you can go to settings and check your Ubuntu version.

Step 2

Next download a Java version from Oracle site

Step 3

Set the path of the terminal to where you downloaded the zip file

Step 4

Use the following command to extract the downloaded file

sudo tar -xvf <your file name>.tar.gz

Step 5

Open /etc/profile file. To do it use the following command

sudo nano /etc/profile

or

sudo gedit /etc/profile

Now enter the following function to the etc/profile file.

JAVA_HOME=<Directory where JAVA has been extracted>/jdk1.8.0
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export PATH

If this not working, enter the following function replacing upper one

export JAVA_HOME=<Directory where JAVA has been extracted>/jdk1.8.0
export PATH=$PATH:$HOME/bin:$JAVA_HOME/bin

Step 6

Now reload the environment

. /etc/profile

Step 7

Now give the location of Java to Ubuntu using following commands

sudo update-alternatives — install “/usr/bin/java” “java” “<Directory where JAVA has been extracted>/bin/java” 1
sudo update-alternatives — install “/usr/bin/javac” “javac” “<Directory where JAVA has been extracted>/bin/javac” 1
sudo update-alternatives — install “/usr/bin/javaws” “javaws” “<Directory where JAVA has been extracted>/bin/javaws” 1

Step 8

Now set the installed version as the default version of java

sudo update-alternatives — set java <Directory where JAVA has been extracted>/bin/java
sudo update-alternatives — set javac <Directory where JAVA has been extracted>/bin/ javac
sudo update-alternatives — set javaws <Directory where JAVA has been extracted>/bin/javaws

Step 9

Verify your Java version with the following command

java -version
javac -version

Now lets install another version of java to Ubuntu machine. In this time lets install openJDK 8 version.

Step 1

get update your apt

sudo apt-get update

Step 2

Now install openJDK 8

sudo apt-get install openjdk-8-jre

Step 3

Set the variables

echo “JAVA_HOME$(which java)” | sudo tee -a /etc/environment

Step 4

Reload the system variables

source /etc/environment

Step 5

Verify variables using this

echo $JAVA_HOME

Now you can check the version of java. You can see that it shows the version as older version(one you installed earlier). But if you need to use version 8, how do you switch to that version. You can use following commands to switch between alternative versions.

sudo update-alternatives — config java

When you run this in terminal it shows us what are the available versions that you can switch on.You can choose the number and after you confirm it, it will be your default java version. You can change your java compiler version with following command.

sudo update-alternatives — config javac