How to install Java JDK in Linux

To install JDK in UBuntu, a simple way is to follow the steps below:

INSTALLING SUN JDK 6 UPDATE 45 ON UBUNTU

1. Download the jdk-6u555-linux-i586.bin from the Sun Java Download Centre. If you are on 64-bit Ubuntu, you should grab jdk-6u555-linux-x64.bin.
2. Make the bin file executable:

   chmod +x jdk-6u555-linux-x64.bin

3. Extract the bin file:

   ./jdk-6u555-linux-x64.bin

4. Move extracted folder to this location:

   sudo mv jdk1.6.0_45 /usr/lib/jvm/

5. Install the new Java source in system:

   sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.6.0_45/bin/javac 1
   sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.6.0_45/bin/java 1
   sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.6.0_45/bin/javaws 1

6. Choose default Java:

   sudo update-alternatives --config javac
   sudo update-alternatives --config java
   sudo update-alternatives --config javaws

7. Check the Java version:

   java -version

8. Verify the symlinks all point to the new Java location:

   ls -la /etc/alternatives/java*

INSTALLING SUN JDK 7 UPDATE 55 ON UBUNTU

1. Download the jdk-7u55-linux-i586.tar.gz from the Sun Java Download Centre. If you are on 64-bit Ubuntu, you should grab jdk-7u55-linux-x64.tar.gz.
2. Extract the tar file:

   tar -xvzf jdk-7u55-linux-x64.tar.gz

3. Move extracted folder to this location:

   sudo mv jdk1.7.0_55 /usr/lib/jvm/

4. Install the new Java source in system:

   sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_55/bin/javac 1
   sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_55/bin/java 1
   sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.7.0_55/bin/javaws 1

5. Choose default Java:

   sudo update-alternatives --config javac
   sudo update-alternatives --config java
   sudo update-alternatives --config javaws

6. Check the Java version:

   java -version

7. Verify the symlinks all point to the new Java location:

   ls -la /etc/alternatives/java*