1. Set JAVA alternative:
sudo update-alternatives --config java
2. Set the environment variables for Java:
2.1 type the command: sudo vim /etc/profile
2.2 Then at the end of the "profile" document, type the following:
#set java environment
export JAVA_HOME=/usr/lib/jvm/java-7-sun
export JRE_HOME=/usr/lib/jvm/java-7-sun/jre
export CLASSPATH=.:$JAVA_HOME/lib:$JRE_HOME/lib:$CLASSPATH
export PATH=$JAVA_HOME/bin:$JRE_HOME/bin:$PATH
2.3 Save the file. And type the following command to apply it immediately:
source /etc/profile
