ubuntu配置java环境

ubuntu系统默认没有安装java环境，当运行javac时提示没有安装：

$ javac
The program 'javac' can be found in the following packages:
 * default-jdk
 * ecj
 * gcj-5-jdk
 * openjdk-8-jdk-headless
 * gcj-4.8-jdk
 * gcj-4.9-jdk
 * openjdk-9-jdk-headless
Try: sudo apt install <selected package>

打开oracle官网，java下载地址

http://www.oracle.com/technetwork/java/javase/downloads/index.html

根据系统选择版本，这里选择 jdk-8u144-linux-x64.tar.gz（Linux x64 176.92 MB)下载好之后，进行解压安装，这里安装到/opt/jdk-8目录下

cd /opt/
mkdir jdk1.8.0_144
cd jdk1.8.0_144/
mv /home/muti/Downloads/jdk-8u144-linux-x64.tar.gz  .
tar -zxvf jdk-8u144-linux-x64.tar.gz 
mv jdk1.8.0_144/* .

然后在/etc/profile中新建java环境变量，

vim /etc/profile

填写内容如下

export JAVA_HOME=/opt/jdk1.8.0_144
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=.:$CLASSPATH:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
export JAVA_HOME=/usr/jdk1.8.0_144
export JRE_HOME=$JAVA_HOME/jre
export CLASSPATH=.:$CLASSPATH:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

立刻生效

source /etc/profile

检查是否正确安装

java -version

输出

# java -version
java version "1.8.0_144"
Java(TM) SE Runtime Environment (build 1.8.0_144-b01)
Java HotSpot(TM) 64-Bit Server VM (build 25.144-b01, mixed mode)