If you are running an older version on java on your Ubuntu 12.04 environment, you must remove it before installing Java7. Do the following to remove:
$sudo apt-get purge openjdk*
If you installed java 7 earlier and having problem with java then you have to do the following to remove it:
$sudo rm /var/lib/dpkg/info/oracle-java7-installer*
$sudo apt-get purge oracle-java7-installer*
$sudo rm /etc/apt/sources.list.d/*java*
$sudo apt-get update
Installing Oracle Java7 on Ubuntu 12.04 LTS:
$sudo add-apt-repository ppa:webupd8team/java
$sudo apt-get update
$sudo apt-get install oracle-java7-installer
You will be prompted couple of times for permissions and Oracle Policy agreement [You must be agreed to Oracle policies to install Java :-)].
That’s it! Now you have Oracle Java7 installed on your Ubuntu 12.04 environment, to check the Java version run the following on terminal:
$java -version
java version "1.7.0_17"
Java(TM) SE Runtime Environment (build 1.7.0_17-b02)
Java HotSpot(TM) 64-Bit Server VM (build 23.7-b01, mixed mode)
Or You can check the java version by searching java in Ubuntu dashboard.
Oracle Java 7 plugin Control Panel -> General Tab -> About
