How To Check Java is already installed in Linux OS

How To Check Java is already installed in Ubuntu Linux

Open a terminal and use the following command:

java -version

If you see an output like the one below, it means you don’t have Java installed:

The program ‘java’ can be found in the following packages:

* default-jre

* gcj-4.6-jre-headless

* openjdk-6-jre-headless

* gcj-4.5-jre-headless

* openjdk-7-jre-headless

Try: sudo apt-get install

 or 

In your terminal type java -version or just javac if it returns something, then you've java installed. Otherwise, there is also the possibility that the path variables do not contain the java path. So uselocate jdk or locate java to see if you have the java binary. Don't forget to run updatedb if you are using locate for the first time.

How To Check Java is already installed in Linux OS