setjdk.bash

function setjdk {
    local ver=${1?Usage: setjdk <version>}
 
    export JAVA_HOME=$(/usr/libexec/java_home -v $ver)
    PATH=$(echo $PATH | tr ':' '\n' | grep -v Java | tr '\n' ':')
    export PATH=$JAVA_HOME/bin:$PATH
}
 
function _setjdk_completion (){
    COMPREPLY=()

    local cur=${COMP_WORDS[COMP_CWORD]//\\\\/}
    local options=$(/usr/libexec/java_home -x | plutil -convert json -r -o - - | grep JVMVersion | sed 's/[^:]*[^"]*"\([^"]*\).*/\1/')
 
    COMPREPLY=($(compgen -W "${options}" ${cur}))
}
 
complete -F _setjdk_completion -o filenames setjdk

setjdk 1.7.0_09

Credit to @martint