suppose you install it in /usr/java/jdk1.7.0/
2.create soft link
#cd /usr/lib64/mozilla/plugins
# ln -s /usr/java/jdk1.7.0/lib/amd64/libnpjp2.so
restart firefox or google chrom,java plugin is enabled.
To disable it,press Tools--> add ons--> select Java(TM) plug-in 1.7.0 ,and then disable it