Java – view jars source code in eclipse

plugin: https://marketplace.eclipse.org/content/java-source-attacher

steps:

1. download the jar.
2. to install, copy jar to {eclipse_folder}/dropins
3. In eclipse in Project explorer > right click in jar > “Attach java source” 😉

Install Java JDK+JRE (oracle) in Kubuntu 13.04 from apt

java -version
sudo apt-get purge openjdk*
sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer
java -version
javac -version

Setting Java environment variables

sudo apt-get install oracle-java7-set-default

source: here 1 and here.