The current version of java-8 may vary. Please adapt the following settings to the current version

Although it has not been tested with this solution, but you can probably use OpenJDK-8. If that is your choice, you can install Java with this command: "sudo apt install openjdk-8-jdk". You can check this page for more instructions: https://linuxize.com/post/install-java-on-ubuntu-18-04/

sudo apt update
sudo apt upgrade
sudo reboot -p -f

sudo mkdir /usr/lib/jvm

cd /usr/lib/jvm
sudo tar xzf /opt/Download/jdk-8u241-linux-x64.tar.gz
sudo ln -s jdk1.8.0_241 current
sudo chown -R root:root jdk1.8.0_241

sudo vi /etc/environment

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/jvm/current/bin:/usr/lib/jvm/current/db/bin:/usr/lib/jvm/current/jre/bin"
J2SDKDIR="/usr/lib/jvm/current"
J2REDIR="/usr/lib/jvm/current/jre"
JAVA_HOME="/usr/lib/jvm/current"

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/current/bin/java" 0
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/current/bin/javac" 0
sudo update-alternatives --set java /usr/lib/jvm/current/bin/java
sudo update-alternatives --set javac /usr/lib/jvm/current/bin/javac

update-alternatives --list java
update-alternatives --list javac

java -version

# Sample answer
java version "1.8.0_241"
Java(TM) SE Runtime Environment (build 1.8.0_241-b07)
Java HotSpot(TM) 64-Bit Server VM (build 25.241-b07, mixed mode)


sudo reboot -f

sudo apt-get update

sudo wget https://www-us.apache.org/dist/maven/maven-3/3.6.3/binaries/apache-maven-3.6.3-bin.tar.gz -P /opt/Download
cd /opt/Download

sudo tar xvzf apache-maven-3.6.3-bin.tar.gz -C /opt
sudo chown -R root:root /opt/apache-maven-3.6.3

sudo vi /etc/profile.d/maven.sh

export JAVA_HOME=/usr/lib/jvm/current
export M3_HOME=/opt/apache-maven-3.6.3
export MAVEN_HOME=/opt/apache-maven-3.6.3
export PATH=${M3_HOME}/bin:${PATH}

sudo chmod +x /etc/profile.d/maven.sh

sudo vi /etc/environment

PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/lib/jvm/current/bin:/usr/lib/jvm/current/db/bin:/usr/lib/jvm/current/jre/bin:/opt/apache-maven-3.6.3/bin"
J2SDKDIR="/usr/lib/jvm/current"
J2REDIR="/usr/lib/jvm/current/jre"
JAVA_HOME="/usr/lib/jvm/current"
MAVEN_HOME="/opt/apache-maven-3.6.3"

If there is a problem, make shure that "/opt/apache-maven-3.6.3" is in $PATH of /etc/environment

source /etc/profile.d/maven.sh
mvn -version

# Sample answer
Maven home: /opt/apache-maven-3.6.3
Java version: 1.8.0_241, vendor: Oracle Corporation, runtime: /usr/lib/jvm/current/jre
Default locale: en, platform encoding: UTF-8
OS name: "linux", version: "5.0.0-1027-azure", arch: "amd64", family: "unix"

cd /opt/Download
sudo wget https://archive.apache.org/dist/lucene/solr/7.7.2/solr-7.7.2.tgz -P /opt/Download

sudo mkdir -p /opt/solr
sudo groupadd solr
sudo useradd -s /bin/bash -g solr -d /opt/solr solr

sudo tar xzf solr-7.7.2.tgz -C /opt
sudo mv /opt/solr-7.7.2/* /opt/solr
sudo chown -R solr:solr /opt/solr

sudo vi /etc/systemd/system/solr.service

[Unit]
Description=Solr 7.7.2 services
After=network.target

[Service]
Type=forking
User=solr
Group=solr

Environment="SOLR_HOME=/opt/solr/server/solr"

ExecStart=/opt/solr/bin/solr start -force
ExecStop=/opt/solr/bin/solr stop

[Install]
WantedBy=multi-user.target

sudo ufw allow 8983/tcp
sudo systemctl daemon-reload
sudo systemctl start solr
sudo systemctl status solr

# Sample answer
● solr.service - Solr 7.7.2 services
   Loaded: loaded (/etc/systemd/system/solr.service; disabled; vendor preset: enabled)
   Active: active (running) since Thu 2019-11-28 12:23:23 UTC; 8s ago
  Process: 116789 ExecStart=/opt/solr/bin/solr start -force (code=exited, status=0/SUCCESS)
 Main PID: 116850 (java)
    Tasks: 41 (limit: 9246)
   CGroup: /system.slice/solr.service
           └─116850 java -server -Xms512m -Xmx512m -XX:NewRatio=3 -XX:SurvivorRatio=4 -XX:TargetSurvivorRatio=90 -XX:MaxTenuringThreshold=8 -XX

nov. 28 12:23:19 vivo-uqam solr[116789]: *** [WARN] *** Your open file limit is currently 1024.
nov. 28 12:23:19 vivo-uqam solr[116789]:  It should be set to 65000 to avoid operational disruption.
nov. 28 12:23:19 vivo-uqam solr[116789]:  If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in
nov. 28 12:23:19 vivo-uqam solr[116789]: *** [WARN] ***  Your Max Processes Limit is currently 30823.
nov. 28 12:23:19 vivo-uqam solr[116789]:  It should be set to 65000 to avoid operational disruption.
nov. 28 12:23:19 vivo-uqam solr[116789]:  If you no longer wish to see this warning, set SOLR_ULIMIT_CHECKS to false in your profile or solr.in
nov. 28 12:23:23 vivo-uqam solr[116789]: [146B blob data]
nov. 28 12:23:23 vivo-uqam solr[116789]: Started Solr server on port 8983 (pid=116850). Happy searching!
nov. 28 12:23:23 vivo-uqam solr[116789]: [14B blob data]
nov. 28 12:23:23 vivo-uqam systemd[1]: Started Solr 7.7.2 services.
lines 1-19/19 (END)

sudo systemctl enable solr
sudo reboot -f
http://x.x.x.x.x:8983/solr/

sudo apt update
sudo apt install git

git --version
# output
git version 2.17.1