Can't remember where I picked this up - but some handy aliases I use for setting java version (given that you have the required version installed):

alias j6='export JAVA_HOME=$(/usr/libexec/java_home -v 1.6)'
alias j7='export JAVA_HOME=$(/usr/libexec/java_home -v 1.7)'
alias j8='export JAVA_HOME=$(/usr/libexec/java_home -v 1.8)'

This handles picking the right version (1.6 from apple, 1.7 and 1.8 from oracle) etc.