I can't install JRE and JDK on my Ubuntu 18.04 LTS

I can't install both the JRE and JDK. First of all, I have not attempted to install the JDK, but I assume that if I did, it wouldn't work because you need to install the JRE.

Second, I can't install the JRE, I have followed a lot of tutorials like https://www.lifewire.com/install-java-on-ubuntu-4125508, and the java and javac commands do not work. It says, Command 'java' not found, but can be installed with: ... and I am not sure what openjdk is. Please help me.

P.S. I have also searched Ask Ubuntu questions, but none of them helped.

P.P.S. Here's the log:

$ sudo apt-get install oracle-java8-installer
sudo apt-get install oracle-java8-installer
Reading package lists... Done
Building dependency tree       
Reading state information... Done
oracle-java8-installer is already the newest version (8u171-1~webupd8~0).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up oracle-java8-installer (8u171-1~webupd8~0) ...
Using wget settings from /var/cache/oracle-jdk8-installer/wgetrc
Downloading Oracle Java 8...
--2018-05-22 05:12:57--  http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz
Resolving download.oracle.com (download.oracle.com)... 23.41.237.84
Connecting to download.oracle.com (download.oracle.com)|23.41.237.84|:80... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: https://edelivery.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz [following]
--2018-05-22 05:12:58--  https://edelivery.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz
Resolving edelivery.oracle.com (edelivery.oracle.com)... 184.87.246.212, 2001:fe0:10:181::2d3e, 2001:fe0:10:195::2d3e
Connecting to edelivery.oracle.com (edelivery.oracle.com)|184.87.246.212|:443... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz?AuthParam=1526937299_29e0412d050d20aa9005e20d76719ea0 [following]
--2018-05-22 05:12:59--  http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz?AuthParam=1526937299_29e0412d050d20aa9005e20d76719ea0
Connecting to download.oracle.com (download.oracle.com)|23.41.237.84|:80... connected.
HTTP request sent, awaiting response... 416 Requested Range Not Satisfiable

    The file is already fully retrieved; nothing to do.

Download done.
Removing outdated cached downloads...
sha256sum mismatch jdk-8u171-linux-x64.tar.gz
Oracle JDK 8 is NOT installed.
dpkg: error processing package oracle-java8-installer (--configure):
 installed oracle-java8-installer package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 oracle-java8-installer
E: Sub-process /usr/bin/dpkg returned an error code (1)
Reading package lists... Done
Building dependency tree       
Reading state information... Done
oracle-java8-installer is already the newest version (8u171-1~webupd8~0).
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue? [Y/n] y
Setting up oracle-java8-installer (8u171-1~webupd8~0) ...
Using wget settings from /var/cache/oracle-jdk8-installer/wgetrc
Downloading Oracle Java 8...
--2018-05-22 05:12:57--  http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz
Resolving download.oracle.com (download.oracle.com)... 23.41.237.84
Connecting to download.oracle.com (download.oracle.com)|23.41.237.84|:80... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: https://edelivery.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz [following]
--2018-05-22 05:12:58--  https://edelivery.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz
Resolving edelivery.oracle.com (edelivery.oracle.com)... 184.87.246.212, 2001:fe0:10:181::2d3e, 2001:fe0:10:195::2d3e
Connecting to edelivery.oracle.com (edelivery.oracle.com)|184.87.246.212|:443... connected.
HTTP request sent, awaiting response... 302 Moved Temporarily
Location: http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz?AuthParam=1526937299_29e0412d050d20aa9005e20d76719ea0 [following]
--2018-05-22 05:12:59--  http://download.oracle.com/otn-pub/java/jdk/8u171-b11/512cd62ec5174c3487ac17c61aaa89e8/jdk-8u171-linux-x64.tar.gz?AuthParam=1526937299_29e0412d050d20aa9005e20d76719ea0
Connecting to download.oracle.com (download.oracle.com)|23.41.237.84|:80... connected.
HTTP request sent, awaiting response... 416 Requested Range Not Satisfiable

    The file is already fully retrieved; nothing to do.

Download done.
Removing outdated cached downloads...
sha256sum mismatch jdk-8u171-linux-x64.tar.gz
Oracle JDK 8 is NOT installed.
dpkg: error processing package oracle-java8-installer (--configure):
 installed oracle-java8-installer package post-installation script subprocess returned error exit status 1
Errors were encountered while processing:
 oracle-java8-installer
E: Sub-process /usr/bin/dpkg returned an error code (1)

edit/P.S. To those who thinks that this is a duplicate, you are mistaken. I am not using a virtual machine, I tried and tried again 'til it succeeded, and it did. My problem now is, the JDK wasn't installed. I found this out when I installed NetBeans and no JDK was installed, but the JRE was installed.