Install JAVA plugin in Firefox in an Redhat Linux box

First, you need make sure you have JAVA installed.
For Redhat, you should use RPM based JAVA installation.

1. Open a terminal, type command "java -version" to make sure that you have the newest JAVA installed.
2. In general, the java should be installed here: /user/java
3. Use following command to make sure you enable JAVA in firefox.
    "ls ~/mozilla/plugins/"
    If it is empty, you need link java to this directory.
4. Use command "ln -s /usr/java/default/jre/lib/amd64/libnpjp2.so ~/.mozilla/plugins/".
5. Be careful if there are many versions of JAVA in /usr/java directory, please use default one. Otherwise you will have conflicts because the firefox can only load one JAVA version.
6. If you have old version in ~/.mozilla/plugins/ directory, you should delete it.
7. Go to JAVA test page: "http://www.java.com/en/download/testjava.jsp", now you should be able to see the JAVA runs now.