Script that I'm using whenever I'm installing new JDK manually.

new-jdk-update-alternatives.sh

#!/bin/bash

JAVA_VERSION=13
JAVA_DIR=/usr/lib/jvm/jdk-${JAVA_VERSION}
PRIORITY=11${JAVA_VERSION}

declare -A ALTERNATIVES_TO_UPDATE
ALTERNATIVES_TO_UPDATE=(
    [jaotc]=bin
    [jar]=bin
    [jarsigner]=bin
    [java]=bin
    [javac]=bin
    [javadoc]=bin
    [javap]=bin
    [jcmd]=bin
    [jconsole]=bin
    [jdb]=bin
    [jdeprscan]=bin
    [jdeps]=bin
    [jexec]=lib
    [jfr]=bin
    [jhsdb]=bin
    [jimage]=bin
    [jinfo]=bin
    [jjs]=bin
    [jlink]=bin
    [jmap]=bin
    [jmod]=bin
    [jps]=bin
    [jrunscript]=bin
    [jshell]=bin
    [jspawnhelper]=lib
    [jstack]=bin
    [jstat]=bin
    [jstatd]=bin
    [keytool]=bin
    [pack200]=bin
    [rmic]=bin
    [rmid]=bin
    [rmiregistry]=bin
    [serialver]=bin
    [unpack200]=bin
)

# update alternative links
for tool in "${!ALTERNATIVES_TO_UPDATE[@]}"
do
    dir=${ALTERNATIVES_TO_UPDATE[$tool]}
    tool_path=$JAVA_DIR/$dir/$tool

    if [ -x $tool_path ]
    then
        sudo update-alternatives --quiet --install /usr/bin/$tool $tool $tool_path $PRIORITY
    else
        echo Skipping $tool_path
    fi
done