If you add functions like these to your .bash_profile then by simply typing the name of the function (in this case java7 or java8) into a terminal session, change the version of Java (or anything else) for just that session. This allows you to have whatever version of Java you need as default but freely switch for one time usage of tools like e.…

.bash_profile

function java7
{
    JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.7.0_21.jdk/Contents/Home
    export JAVA_HOME
}

function java8
{
    JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0.jdk/Contents/Home
    export JAVA_HOME
}