Detect Java Installation with Shell Script

#!/bin/bash
# This script attempts to find an existing installation of Java that meets a minimum version
# requirement on a Linux machine.  If it is successful, it will export a JAVA_HOME environment
# variable that can be used by another calling script.
#
# To specify the required version, set the REQUIRED_VERSION to the major version required, 
# e.g. 1.3, but not 1.3.1.
REQUIRED_VERSION=1.5

# Transform the required version string into a number that can be used in comparisons
REQUIRED_VERSION=`echo $REQUIRED_VERSION | sed -e 's;\.;0;g'`
# Check JAVA_HOME directory to see if Java version is adequate
if [ $JAVA_HOME ]
then
     JAVA_EXE=$JAVA_HOME/bin/java
     $JAVA_EXE -version 2> tmp.ver
     VERSION=`cat tmp.ver | grep "java version" | awk '{ print substr($3, 2, length($3)-2); }'`
     rm tmp.ver
     VERSION=`echo $VERSION | awk '{ print substr($1, 1, 3); }' | sed -e 's;\.;0;g'`
     if [ $VERSION ]
     then
          if [ $VERSION -ge $REQUIRED_VERSION ]
          then
               JAVA_HOME=`echo $JAVA_EXE | awk '{ print substr($1, 1, length($1)-9); }'`
          else
               JAVA_HOME=
          fi
     else
          JAVA_HOME=
     fi
fi

# If the existing JAVA_HOME directory is adequate, then leave it alone
# otherwise, use 'locate' to search for other possible java candidates and
# check their versions.
if [ $JAVA_HOME ]
then
     :
else
     for JAVA_EXE in `locate bin/java | grep java$ | xargs echo`
     do
          if [ $JAVA_HOME ] 
          then
               :
          else
               $JAVA_EXE -version 2> tmp.ver 1> /dev/null
               VERSION=`cat tmp.ver | grep "java version" | awk '{ print substr($3, 2, length($3)-2); }'`
               rm tmp.ver
               VERSION=`echo $VERSION | awk '{ print substr($1, 1, 3); }' | sed -e 's;\.;0;g'`
               if [ $VERSION ]
               then
                    if [ $VERSION -ge $REQUIRED_VERSION ]
                    then
                         JAVA_HOME=`echo $JAVA_EXE | awk '{ print substr($1, 1, length($1)-9); }'`
                    fi
               fi
          fi
     done
fi

# If the correct Java version is detected, then export the JAVA_HOME environment variable
if [ $JAVA_HOME ]
then
     export JAVA_HOME
     echo $JAVA_HOME
fi