# on linux
sudo update-alternatives --config java
# then just input the number of the jdk you
# want to use as default and hit Enter/usr/libexec/java_home -V
export JAVA_HOME=`/usr/libexec/java_home -v 1.6.0_65-b14-462` //java 8
Matching Java Virtual Machines (3):
1.8.0_05, x86_64: "Java SE 8" /Library/Java/JavaVirtualMachines/jdk1.8.0_05.jdk/Contents/Home
1.6.0_65-b14-462, x86_64: "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
1.6.0_65-b14-462, i386: "Java SE 6" /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home
/Library/Java/JavaVirtualMachines/jdk1.8.0_05.jdk/Contents/Home