Java Runtime Environment (JRE) not found (linux ubuntu)

I just install java following the easy to follow guide: https://www.java.com/en/download/help/linux_x64_install.xml.

So by step I:

1) Downloaded jre-8u221-linux-x64(1).tar.gz from my browser (ubunto Gnome)

2) I moved it to my desired path so: /:mv jre-8u221-linux-x64(1).tar.gz /usr/java

3) I changed permission on it /:sudo chmod 777 jre-8u221-linux-x64(1).tar.gz

4) Unzip it: tar zxvf jre-8u73-linux-x64.tar.gz

5) Now done.

If I do a: java -version I obtain:

The program 'java' can be found in the following packages:
* default-jre
* gcj-5-jre-headless
* openjdk-8-jre-headless

* gcj-4.8-jre-headless
* gcj-4.9-jre-headless
* openjdk-9-jre-headless
Try: apt install

As if my java is not detected even if it"s installed...

root@:/usr/java#:ls
bin lib plugin THIRDPARTYLICENSEREADME-JAVAFX.txt

COPYRIGHT LICENSE README THIRDPARTYLICENSEREADME.txt
jre1.8.0_221 man release Welcome.html

root@:/usr/java#:cd jre1.8.0_221/

root@:/usr/java/jre1.8.0_221/#:ls
bin lib man README THIRDPARTYLICENSEREADME-JAVAFX.txt Welcome.html
COPYRIGHT LICENSE plugin release THIRDPARTYLICENSEREADME.txt

root@:/usr/java/jre1.8.0_221/#:cd bin

root@:/usr/java/jre1.8.0_221/bin/#:ls
ControlPanel javaws jjs orbd policytool rmiregistry tnameserv
java jcontrol keytool pack200 rmid servertool unpack200

As we can see java is here (/usr/java/jre1.8.0_221/bin/java)

So I don't know what to do, my programs don't detect my java until I define the path and when I execute java -version the version is not detected...

Please help

Answer

Edit your ~/.bashrc file and add the following lines:

export JAVA_HOME=/usr/java/
export PATH=$PATH:$JAVA_HOME/bin
export JRE_HOME=/usr/java/jre1.8.0_221 

Save the changes, exit and restart your bash shell.

Type in java -version to check if it has worked.