set mac jdk version to 1.8

To set Java to 1.8 for your shell environment, put this in your ~/.bash_profile:

export JAVA_HOME=`/usr/libexec/java_home -v 1.8`

Solution without 3rd party tools:

leave all JDKs at their default location, under /Library/Java/JavaVirtualMachines. The system will pick the highest version by default. To exclude a JDK from being picked by default, rename its Contents/Info.plist to Info.plist.disabled. That JDK can still be used when $JAVA_HOME points to it, or explicitly referenced in a script or configuration. It will simply be ignored by system's java command. System launcher will use the JDK with highest version among those that have an Info.plist file.

When working in a shell with alternate JDK, pick your method among existing answers (jenv, or custom aliases/scripts around /usr/libexec/java_home, etc).