debian9安装jdk1.8
//先跟新可用安装信息
apt-get update
//查看可以安装的jdk版本
apt-cache search jdk
//会显示如下内容：
openjdk-8-dbg - Java runtime based on OpenJDK (debugging symbols)
openjdk-8-demo - Java runtime based on OpenJDK (demos and examples)
openjdk-8-doc - OpenJDK Development Kit (JDK) documentation
openjdk-8-jdk - OpenJDK Development Kit (JDK)
openjdk-8-jdk-headless - OpenJDK Development Kit (JDK) (headless)
openjdk-8-jre - OpenJDK Java runtime, using Hotspot JIT
openjdk-8-jre-headless - OpenJDK Java runtime, using Hotspot JIT (headless)
openjdk-8-jre-zero - Alternative JVM for OpenJDK, using Zero/Shark
openjdk-8-source - OpenJDK Development Kit (JDK) source files
openjdk-8-jre-dcevm - Alternative VM for OpenJDK 8 with enhanced class redefinition
//选择需要安装的版本:
apt-get install openjdk-8-jdk
//等待安装完成，验证是否完成安装
java -version
//显示如下信息，确定完成安装。
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-8u232-b09-1~deb9u1-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)