Linux CentOS 卸载1.7JDK 安装1.8JDK_centos卸载jdk1.7-优快云博客

参考文章：

https://blog.youkuaiyun.com/qq_24641227/article/details/90112710
参考视频: 韩顺平 linux 基础
https://www.bilibili.com/video/BV1Sv411r7vd?p=86

准备工作，如果有 jdk 7 ,jdk 8 ，先行删除

java -version ==》本机显示 “1.8.0_181”
到网站上面下载 jdk8 https://www.oracle.com/java/technologies/javase/javase-jdk8-downloads.html ,当前版本 jdk-8u281-linux-x64.tar.gz
>(通过lrzsz rz 指令 )将文件上传到Linux 虚拟机 192.168.121.37 上面 /opt/jdk 目录

删除本地java 过程

[root@shell37 software]# java -version
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
[root@shell37 alternatives]# which java
/usr/bin/java
[root@shell37 alternatives]# rm -rf /usr/bin/java
[root@shell37 alternatives]# which java
/usr/local/java/jdk1.8.0_251/bin/java
[root@shell37 alternatives]# rm -rf /usr/local/java/jdk1.8.0_251/
[root@shell37 alternatives]# which java

[root@shell37 alternatives]# java -version                         
-bash: /usr/bin/java: No such file or directory
[root@shell37 alternatives]# java
-bash: /usr/bin/java: No such file or directory
[root@shell37 alternatives]# javac
bash: javac: command not found...


[root@shell37 software]# vim /etc/profile   ---可以暂时不用修改 
export JAVA_HOME=/usr/local/java/jdk1.8.0_251
export JRE_HOME=/usr/local/java/jdk1.8.0_251/jre
export CLASSPATH=.:$CLASSPATH:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

------------打印环境变量 
[root@shell37 software]# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin ....

安装步骤：

1.mkdir /opt/jdk — 新建目录用于存放安装文件
2.上传文件到/opt/jdk目录下
3.进入/opt/jdk 目录下，执行解压操作 tar -zxvf jdk-8u281-linux-x64.tar.gz
4.mkdir /usr/local/java -------------------新建目录用于安装软件
5.mv /opt/jdk/jdk1.8.0_281 /usr/local/java/ —将解压好的文件放到指定目录
6.vim /etc/profile ------------------配置环境变量
6.1 export JAVA_HOME=/usr/local/java/jdk1.8.0_281
6.2 export PATH= $JAVA_HOME/bin:$ PATH
7. source /etc/profile -----------------让文件生效
8. vim test1.java javac test1.java java test1

安装步骤详解

[root@shell37 jdk]# ll /opt/jdk
total 140356
-rw-r--r--. 1 root root 143722924 Mar 21 00:26 jdk-8u281-linux-x64.tar.gz

[root@shell37 jdk]# tar -zxvf jdk-8u281-linux-x64.tar.gz 
[root@shell37 jdk]# ll
total 140356
drwxr-xr-x. 8 10143 10143       273 Dec  9 04:50 jdk1.8.0_281
-rw-r--r--. 1 root  root  143722924 Mar 21 00:26 jdk-8u281-linux-x64.tar.gz

[root@shell37 jdk]# mv /opt/jdk/jdk1.8.0_281/ /usr/local/java/
[root@shell37 jdk]# ll /usr/local/java
total 0
drwxr-xr-x. 8 10143 10143 273 Dec  9 04:50 jdk1.8.0_281

-----编辑 环境变量配置文件，通常是将下面脚本 放到/etc/profile最后面 
[root@shell37 software]# vim /etc/profile
export JAVA_HOME=/usr/local/java/jdk1.8.0_281
export JRE_HOME=/usr/local/java/jdk1.8.0_281/jre
export CLASSPATH=.:$CLASSPATH:$JAVA_HOME/lib:$JRE_HOME/lib
export PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin

------编辑保存 /etc/profile 后，查看是否配置成功，没有，需要执行source 指令后方可以生效。
[root@shell37 software]# java -version
bash: java: command not found...
[root@shell37 software]# source /etc/profile
[root@shell37 software]# java -version
java version "1.8.0_281"
Java(TM) SE Runtime Environment (build 1.8.0_281-b09)
Java HotSpot(TM) 64-Bit Server VM (build 25.281-b09, mixed mode)

----- 编译测试安装的java版本是否可用

[root@shell37 opt]# vim Hello.java 
public class Hello{
   public static void main(String[] args){
          System.out.println("hello");
    }
}

[root@shell37 opt]# javac Hello.java 
[root@shell37 opt]# ll
-rw-r--r--. 1 root root     409 Mar 21 00:43 Hello.class
-rw-r--r--. 1 root root     110 Mar 21 00:42 Hello.java
-rw-r--r--. 1 root root      83 Mar 18 22:18 time.sh
[root@shell37 opt]# java Hello
hello