Install Java JDK on Ubuntu
OpenJDK Installation
Installing the Default OpenJDK (Java 11)
#First, update the apt package index with:
sudo apt update
#install the default Java OpenJDK package with:
sudo apt install default-jdk
#Verify the installation
java -version
Installing OpenJDK 8
sudo apt update
sudo apt install openjdk-8-jdk
Installing Oracle Java
# Install the dependencies necessary to add a new repository:
sudo apt install software-properties-common
# Enable the Linux Uprising PPA
sudo add-apt-repository ppa:linuxuprising/java
# update the packages list and install the oracle-java11-installer
sudo apt update
sudo apt install oracle-java11-installer
# accept the Oracle license & Verify the installation.
java -version
Set the Default Java Version
If you have multiple Java installations to change the default version, use the update-alternatives tool
sudo update-alternatives --config java
#To change the default Java version just enter the version number (the number in the Selection column) and press Enter.
Set the JAVA_HOME Environment Variable
To set the JAVA_HOME environment variable, first, you need to find out the Java installation paths using the update-alternatives command
sudo update-alternatives --config java
# Copy the installation path & open the /etc/environment file:
sudo nano /etc/environment
# Add the following line, at the end of the file:
JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64"
# Run 'source' command to apply the changes
source /etc/environment
# To verify that the JAVA_HOME run echo command:
echo $JAVA_HOME
if you want to uninstall the openjdk-8-jdk package run:
sudo apt remove openjdk-8-jdk
Install JDK on CentOS
Installing OpenJDK 11
#install java11
sudo yum install java-11-openjdk-devel
#verify
java -version
# To install only the headless OpenJDK 11 type(minimal Java runtime):
sudo yum install java-11-openjdk-headless
Installing OpenJDK 8
# install 1.8
sudo yum install java-1.8.0-openjdk-devel
# Verify the installation
java -version
# Setting the Default Java Version
sudo alternatives --config java