Install JDK

• Download JDK

  1. Visit to Oracle Java SE download page.
  2. Download JDK for Linux 64 such as jdk-8u91-linux-x64.tar.gz.

• Check if we have Java installed on our system

  1. Open the Terminal
  2. Type java -version.

  If we have OpenJDK installed:

  java version "1.7.0_15"
  OpenJDK Runtime Environment (IcedTea6 1.10pre) (7b15~pre1-0lucid1)
  OpenJDK 64-Bit Server VM (build 19.0-b09, mixed mode)
  

• Copy .gz to destination folder

  1. cd /home/"our_user_name"/Downloadssuch ascd /home/yen/Downloads.
  2. sudo cp -r jdk-8u91-linux-x64.tar.gz /usr/local/java

• Unpack the .gz

  1. cd /usr/local/java
  2. sudo tar xvzf jdk-8u91-linux-x64.tar.gz

• Edit the system PATH file

  1. sudo gedit /etc/profile
  2. Scroll down to the end of the file.
  3. add the following lines below:

     JAVA_HOME=/usr/local/java/jdk1.8.0_91
     JRE_HOME=$JAVA_HOME/jre
     PATH=$PATH:$JRE_HOME/bin:$JAVA_HOME/bin
     export JAVA_HOME
     export JRE_HOME
     export PATH
     

• Inform system where the Oracle Java JDK/JRE is

  sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.8.0_91/bin/java" 1
  sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.8.0_91/bin/javac" 1
  sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.8.0_91/bin/javaws" 1
  

• Set it to be default

  sudo update-alternatives --set java /usr/local/java/jdk1.8.0_91/bin/java
   sudo update-alternatives --set javac /usr/local/java/jdk1.8.0_91/bin/javac
   sudo update-alternatives --set javaws /usr/local/java/jdk1.8.0_91/bin/javaws
  

• Reload system wide PATH /etc/profile

  source /etc/profile

• Double check

  1. java -version

     java version "1.8.0_91"
     Java(TM) SE Runtime Environment (build 1.8.0_91-b14)
     Java HotSpot(TM) 64-Bit Server VM (build 25.91-b14, mixed mode)
     

  2. javac -version

     javac 1.8.0_91

  3. We can write a simple java class to test.

• Restart Ubuntu

Install JDK in Ubuntu