MacOS version handling

java-functions.sh

function removeFromPath() {
   export PATH=$(echo ${PATH} | sed -E -e "s;:$1;;" -e "s;$1:?;;")
}

function showJdk() {
   /usr/libexec/java_home
}

function setJdk() {
  if [ $# -ne 0 ]; then
    removeFromPath '/System/Library/Frameworks/JavaVM.framework/Home/bin'
    if [ -n "${JAVA_HOME+x}" ]; then
       removeFromPath ${JAVA_HOME}/bin
    fi
    export JAVA_HOME=`/usr/libexec/java_home -v $@`
    export PATH=${JAVA_HOME}/bin:${PATH}

    echo ""
    java -version
    echo ""
  fi
}

function listJdks() {
  /usr/libexec/java_home -V
}

if [ -f /usr/libexec/java_home ]; then
  export HISTORY=10000
  echo ""
  echo "Settings JDK ..."
  setJdk 1.8
else
  echo ""
  echo -n "Configured Jdk is "
  java -version
  javac -version
  echo ""
fi

Usage.sh

$ listJdks 
Matching Java Virtual Machines (3):
    1.8.0_151, x86_64:	"Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home
    1.8.0_77, x86_64:	"Java SE 8"	/Library/Java/JavaVirtualMachines/jdk1.8.0_77.jdk/Contents/Home
    1.7.0_80, x86_64:	"Java SE 7"	/Library/Java/JavaVirtualMachines/jdk1.7.0_80.jdk/Contents/Home

/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home

$ showJdk 
/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home

$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home

$ setJdk 1.7 

java version "1.7.0_80"
Java(TM) SE Runtime Environment (build 1.7.0_80-b15)
Java HotSpot(TM) 64-Bit Server VM (build 24.80-b11, mixed mode)

$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.7.0_80.jdk/Contents/Home

$ setJdk 1.8 

java version "1.8.0_151"
Java(TM) SE Runtime Environment (build 1.8.0_151-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.151-b12, mixed mode)

$ echo $JAVA_HOME
/Library/Java/JavaVirtualMachines/jdk1.8.0_151.jdk/Contents/Home

$