Jocodoma

Completely Uninstall and Reinstall OpenJDK

If you are trying to remove OpenJDK 6, try

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sudo apt-get remove openjdk-6-jdk

or,

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sudo apt-get remove default-jdk

apt-cache search only shows you available packages, not the packages you have installed. For that, try

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sudo dpkg --list

The following command will show any JDK-related packages installed on your system.

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sudo dpkg --list | grep -i jdk

Reference:
http://askubuntu.com/questions/139702/completely-uninstall-and-reinstall-openjdk

Switch Default Java Version in Ubuntu

update-alternatives does a great job switching the default java version, just in case you haven’t known it:

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sudo update-alternatives --config java

Reference:
http://stackoverflow.com/questions/12836666/how-to-remove-open-jdk-completely-in-ubuntu

Kill and Logout Users in pts/* Linux

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skill -KILL -v pts/1

Reference:
http://servercomputing.blogspot.com/2012/01/kill-and-logout-users-in-pts-linux.html

Install Oracle Java on Ubuntu 12.04

Issue following commands:

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sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update

Install java 7:

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sudo apt-get install oracle-java7-installer

or, if you want to have java 6 (e.g. for building android):

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sudo apt-get install oracle-java6-installer

Check if installed successfully:

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java -version

Reference:
http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html

sudo in scripts

using sudo in the script

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sudo -u user1 command1