Bashscript to install legacy JDK on Debian/Ubuntu

#!/bin/bash
#script to install legacy java on a debian/ubuntu box
#Author: Jan Kapellen

usage() {
        echo "Usage: $0 /path/to/java/dir"
        exit 1
}

[[ $# -eq 0 ]] && usage

PRIO=1065

JAVA=$1/bin/java
if [[ -f $JAVA ]]
then
        echo -n "installing java version "
        $JAVA -version
        BINPATH=$1/bin
        for bin in `ls -1 $BINPATH`
        do
                FULLBIN=$BINPATH/$bin
                EFFBIN=`which $bin`
                if [[ $EFFBIN != "" ]]
                then
                        #echo "$FULLBIN -> $EFFBIN -> $bin"
                        update-alternatives --install $EFFBIN $bin $FULLBIN $PRIO
                        update-alternatives --config $bin
                fi
        done
        echo "checking for java-plugin ..."
        PLUG=`find $1 -type f -name libnpjp2.so`
        if [[ $PLUG != "" ]]
        then
                update-alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so mozilla-javaplugin.so $PLUG $PRIO
                update-alternatives --config mozilla-javaplugin.so
        else
                echo "no plugin found, skipping plugin!"
        fi

else
        echo "java binary not found in directory! exiting ..."
        exit 1
fi