Switching Between JDK Versions

I use the init-java-env script described here to switch between different JDK versions. After the installation/unpacking of the different JDKs under a common parent folder (e.g. /use/local/java), the script bellow can be used to set JAVA_HOME and put JAVA_HOME/bin in the PATH. Let say you have installed JDK 1.5 and JDK 1.6 at /usr/local/java/jdk1.5.0_13 and /use/local/java/jdk1.6.0_03 respectively, than execute the script like this to switch between the JDK versions:

source /usr/local/java/init-java-env jdk1.6
source /usr/local/java/init-java-env jdk1.5

Here comes the script:

#!/bin/bash
#

function get_script_location() {
 if [[ "$0" == *"init-java-env" ]]; then
   echo 
   echo " *************************************"
   echo "   Should be called for sourcing only:"
   echo "          source $0"
   echo "   or"
   echo "          . $0"
   echo 
   exit 1
 fi

 local script_loc=$(history 1)
 if [ -z "$script_loc" ] ; then script_loc="${BASH_SOURCE[0]}" ; fi

 script_loc=${script_loc#*. }
 script_loc=${script_loc#*source }
 script_loc=${script_loc%% }
 script_loc=$(eval echo $script_loc)
 script_loc=$(readlink -f "$script_loc")
 script_loc=$(dirname "$script_loc")

 eval "$1=$script_loc"
}

function get_java_home {
 local script_dir=""
 local java_version=$2 
 get_script_location script_dir
 local _jh=$(find $script_dir -maxdepth 1 -name "*$java_version*"  -printf '%p')

 if [ -z "$_jh" ]; then
  echo "Cannot find Java $java_version under $script_dir"
 else 
  _jh=${_jh/\.\//$(pwd)/}
  eval "$1=$_jh"
 fi
}

function init_java_env {
 local java_version="jdk1.5"
 [ $# == 0 ] || java_version="$1"

 local java_home_in_path="`which java`"
 [ "$java_home_in_path" == "" ] || java_home_in_path="$(dirname $(dirname $java_home_in_path))"
 local java_home="$java_home_in_path"

 get_java_home java_home $java_version
 echo "Found Java at: $java_home"


 if [ "$java_home" == "$JAVA_HOME" ] && [ "$java_home" == "$java_home_in_path" ]; then
  echo "JAVA_HOME is already set to: $JAVA_HOME"
 else
  # remove JAVA_HOME/bin from PATH
  if [ -n "$JAVA_HOME" ]; then
    echo "removing $JAVA_HOME/bin from $PATH"
    export PATH=${PATH/$JAVA_HOME\/bin:/}
    export PATH=${PATH/$JAVA_HOME\/bin/}
  fi
  export JAVA_HOME="$java_home"

  export PATH=$JAVA_HOME/bin:$PATH
  echo "Using Java $JAVA_VERSION at JAVA_HOME: $JAVA_HOME"
 fi
}


init_java_env $@