java8 base image base on ubuntu:20.04: include jre, jdk/bin, jdk/lib/tools.jar

Teste

Essential Ubuntu 16.04 + Oracle Java 8 without optional mission control or visualvm

Ubuntu-based image with Java 8, Maven and LaTeX.

Openjdk-8-jdk installed on ubuntu bionic base image with apt repository.

镜像内包含jdk1.8，可作为java项目的基础镜像