rJava installation problem : libjvm.so: cannot open shared object file: No such file or directory

export LD_LIBRARY_PATH=/usr/lib/jvm/java-8-oracle/jre/lib/amd64/server
or
export LD_LIBRARY_PATH=/usr/lib/jvm/java-8-oracle/jre/lib/amd64/server

then 
R CMD javareconf
or
R CMD javareconf -e

from : http://askubuntu.com/questions/584529/libjvm-so-cannot-open-shared-object-file-no-such-file-or-directory