I installed oracle-jdk8. If you need,

sudo add-apt-repository ppa:webupd8team/java && sudo apt update
sudo apt install oracle-java8-installer

The best way to do this is to use update alternatives not using JAVA_HOME. I downloaded the latest tarball jdk-8u162-linux-x64.tar.gz into a subdirectory ./src. I've also set up /opt so that it is owned by me, otherwise you need to use sudo for the untarring of the .tar.gz file.

#!/usr/bin/env bash

MAJOR_VERSION=8
ORACLE_BUILD_VERSION=162

JDK_TARBALL_VERSION=8u${ORACLE_BUILD_VERSION}-linux-x64
JDK_VERSION=1.${MAJOR_VERSION}.0_${ORACLE_BUILD_VERSION}
PRIORITY="10${MAJOR_VERSION}1"

cd src && tar xzf jdk-${JDK_TARBALL_VERSION}.tar.gz -C /opt/jdk

sudo update-alternatives --install /usr/bin/java java /opt/jdk/jdk${JDK_VERSION}/bin/java ${PRIORITY}
sudo update-alternatives --install /usr/bin/javac javac /opt/jdk/jdk${JDK_VERSION}/bin/javac ${PRIORITY}

echo "Checking: alternatives on java and javac"
sudo update-alternatives --display java
sudo update-alternatives --display javac

echo "Running: java -version"
java -version

I've included build 162 since this is much more recent that 45 in your message. This script above should be provided to everyone in the field of development since we can see currently that oracle-java8-installer for Debian and Ubuntu is broken as of yesterday. It might be fixed in a few days but this script will always work.

The priority value in the script is really important since you must override existing priority of the installed package. I've set it to use the major version to be installed. This priority would only fail if you have openjdk version 9 installed.