In this article we are going to see installation process of Java. By mean of Java, I am referring JDK which comes with JRE. This blog has been update with new versions of java.

What is Java?

Java introduced as programming language, which has its own runtime environment(named JRE) that runs java applications on top of JVM(java virtual machine)

Java Installation in windows

Download & install

For Open JDK : Download from here and follow Gui Instructions
For Graal VM : Download from here and follow Gui Instructions
For Oracle JDK : Download from here and follow Gui Instructions

Make sure you choose windows 64bit

Configure Java

Open System variables windows
- either : Start -> Control Panel-> System -> Advanced system settings -> Advanced ->Environment Variables -> System variables
- or , press windows key and type edit the system environment variables & press enter.
In system variables section , click New and add following variable names with values.
- java.version, C:\Program Files\Java\jdk1.8.0_231
- JAVA_HOME, C:\Program Files\Java\jdk1.8.0_231
- JDK_HOME, C:\Program Files\Java\jdk1.8.0_231
Open Path variable
Click New
type %JAVA_HOME%\bin and press ok , this will add java in path variable. Note : My java installation path is “C:\Program Files\Java\jdk1.8.0_231”, if it is different than your’s , please use that.

Java Installation in Ubuntu

For Open JDK8 :

    sudo apt-get update && sudo apt-get install openjdk-8-jdk ### For Open JDK13 : 
  
    sudo apt-get update && sudo apt-get install openjdk-13-jdk

For Graal VM :

Download from here for ubuntu

Unzip

  tar -xvzf graalvm-ce-1.0.0-rc14-linux-amd64.tar.gz

More files to proper directory

  mv graalvm-ce-1.0.0-rc14/ /usr/lib/jvm/
  cd /usr/lib/jvm
  ln -s graalvm-ce-1.0.0-rc14 graalvm

if you have multiple version installed in pc, choose correct Java version
```
  alternatives --config java
```

now choose your GraalVM java , like me if you had 3 java, and graal is no3, so you can install like this.

    alternatives --install /usr/bin/java java /usr/lib/jvm/graalvm/bin/java 3

For Oracle JDK13 :

    sudo apt-get update && sudo apt-get install -y software-properties-common
    sudo add-apt-repository ppa:linuxuprising/java
    sudo apt-get update && sudo apt-get install -y oracle-java13-installer

Installation does not mean you can use in command line. You need to add certain environment variable then you can

Configure Environment

Java to OS’s PATH. Keep the java’s bin directory path in the operation system’s path .It will help a OS to find the commands.

Ubuntu

This will add in path variable

  export JAVA_HOME=/usr/lib/jvm/openjdk-13-jdk
  export PATH=$PATH:$JAVA_HOME/bin

if open JDK 8 , change name “openjdk-13-jdk” to “openjdk-8-jdk”

For CentOS(old post) :

In CentOS the folder /etc/profile.d/ is the recommended place to add customizations to the system profile(adding path). While installing the Sun JDK, you might set the JAVA_HOME and JRE_HOME environment variables. For that

Create a new file called java.sh(its a shell script that sets the environment variable)
```
  vim /etc/profile.d/java.sh
```

In the file, we need to add environment variable initialization commands.

    export JRE_HOME=/usr/java/jdk1.5.0_12/jre
    export PATH=$PATH:$JRE_HOME/bin
    export JAVA_HOME=/usr/java/jdk1.5.0_12
    export JAVA_PATH=$JAVA_HOME
    export PATH=$PATH:$JAVA_HOME/bin

Now when you restart(to load profile.d file ) . Note : If you do not want rebooting, you have run source command

    source java.sh

Test Installation

Open Commandline and type
```
  java -version 
```

You should be able to see java version details.

java-installation