linux下安装OpenJDK 1.8

1. 使用yum查找jdk: yum search java|grep jdk

[root@iasdasd jvm]# yum search java|grep jdk
Repository extras is listed more than once in the configuration
Repository PowerTools is listed more than once in the configuration
Last metadata expiration check: 2:11:26 ago on Wed 09 Feb 2022 07:18:56 PM CST.
java-1.8.0-openjdk.x86_64 : OpenJDK 8 Runtime Environment
java-1.8.0-openjdk-accessibility.x86_64 : OpenJDK 8 accessibility connector
java-1.8.0-openjdk-demo.x86_64 : OpenJDK 8 Demos
java-1.8.0-openjdk-devel.x86_64 : OpenJDK 8 Development Environment
java-1.8.0-openjdk-headless.x86_64 : OpenJDK 8 Headless Runtime Environment
java-1.8.0-openjdk-headless-slowdebug.x86_64 : OpenJDK 8 Runtime Environment unoptimised with full debugging on
java-1.8.0-openjdk-javadoc.noarch : OpenJDK 8 API documentation
java-1.8.0-openjdk-javadoc-zip.noarch : OpenJDK 8 API documentation compressed in a single archive
java-1.8.0-openjdk-slowdebug.x86_64 : OpenJDK 8 Runtime Environment unoptimised with full debugging on
java-1.8.0-openjdk-src.x86_64 : OpenJDK 8 Source Bundle
java-11-openjdk.x86_64 : OpenJDK 11 Runtime Environment
java-11-openjdk-demo.x86_64 : OpenJDK 11 Demos
java-11-openjdk-devel.x86_64 : OpenJDK 11 Development Environment
java-11-openjdk-headless.x86_64 : OpenJDK 11 Headless Runtime Environment
java-11-openjdk-javadoc.x86_64 : OpenJDK 11 API documentation
java-11-openjdk-javadoc-zip.x86_64 : OpenJDK 11 API documentation compressed in a single archive
java-11-openjdk-jmods.x86_64 : JMods for OpenJDK 11
java-11-openjdk-src.x86_64 : OpenJDK 11 Source Bundle
java-11-openjdk-static-libs.x86_64 : OpenJDK 11 libraries for static linking
java-17-openjdk.x86_64 : OpenJDK 17 Runtime Environment
java-17-openjdk-demo.x86_64 : OpenJDK 17 Demos
java-17-openjdk-devel.x86_64 : OpenJDK 17 Development Environment
java-17-openjdk-headless.x86_64 : OpenJDK 17 Headless Runtime Environment
java-17-openjdk-javadoc.x86_64 : OpenJDK 17 API documentation
java-17-openjdk-javadoc-zip.x86_64 : OpenJDK 17 API documentation compressed in a single archive
java-17-openjdk-jmods.x86_64 : JMods for OpenJDK 17
java-17-openjdk-src.x86_64 : OpenJDK 17 Source Bundle
java-17-openjdk-static-libs.x86_64 : OpenJDK 17 libraries for static linking

2. 执行安装命令：yum install java-1.8.0-openjdk

安装成功后，默认安装路径在/usr/lib/jvm/下边，
如/usr/lib/jvm/java-1.8.0-openjdk-1xxxxxxxx 每个人的可能不同，下面配置环境会用到这个路径，要记住，

查看安装路径(如下所示)：
which java
ls -lrt /usr/bin/java

[root@preproduct1 ~]# which java
/usr/bin/java
[root@preproduct1 ~]# echo $JAVA_HOME
/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.191.b12-1.el7_6.x86_64
[root@preproduct1 ~]# ls -lrt /usr/bin/java
lrwxrwxrwx 1 root root 22 Feb 13 10:40 /usr/bin/java -> /etc/alternatives/java
[root@preproduct1 ~]# ls -lrt /etc/alternatives/java
lrwxrwxrwx 1 root root 73 Feb 13 10:40 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.191.b12-1.el7_6.x86_64/jre/bin/java
[root@preproduct1 ~]# cd /usr/lib/jvm
[root@preproduct1 /usr/lib/jvm]# ll
total 4
lrwxrwxrwx 1 root root   26 Feb 13 10:44 java -> /etc/alternatives/java_sdk
lrwxrwxrwx 1 root root   32 Feb 13 10:44 java-1.8.0 -> /etc/alternatives/java_sdk_1.8.0
lrwxrwxrwx 1 root root   40 Feb 13 10:44 java-1.8.0-openjdk -> /etc/alternatives/java_sdk_1.8.0_openjdk
drwxr-xr-x 7 root root 4096 Feb 13 10:44 java-1.8.0-openjdk-1.8.0.191.b12-1.el7_6.x86_64
lrwxrwxrwx 1 root root   34 Feb 13 10:44 java-openjdk -> /etc/alternatives/java_sdk_openjdk
lrwxrwxrwx 1 root root   21 Feb 13 10:40 jre -> /etc/alternatives/jre
lrwxrwxrwx 1 root root   27 Feb 13 10:40 jre-1.8.0 -> /etc/alternatives/jre_1.8.0
lrwxrwxrwx 1 root root   35 Feb 13 10:40 jre-1.8.0-openjdk -> /etc/alternatives/jre_1.8.0_openjdk
lrwxrwxrwx 1 root root   51 Feb 13 10:40 jre-1.8.0-openjdk-1.8.0.191.b12-1.el7_6.x86_64 -> java-1.8.0-openjdk-1.8.0.191.b12-1.el7_6.x86_64/jre
lrwxrwxrwx 1 root root   29 Feb 13 10:40 jre-openjdk -> /etc/alternatives/jre_openjdk

3 验证java是否安装成功

• 查看java版本：java -version

• # java -version
  openjdk version "1.8.0_191"
  OpenJDK Runtime Environment (build 1.8.0_191-b12)
  OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)
  

• 查看java是否可用：javac

• # javac
  -bash: javac: command not found
  

  　　错误原因：默认安装完只有运行环境，java安装目录下只有jre文件夹
  
  

  4 安装开发环境
  
  

  yum install java-1.8.0-openjdk-devel.x86_64
  

  再次输入javac说明安装成功

  5 设置环境变量

  修改/etc/profile文件：vi /etc/profile

  在profile文件末尾新增如下内容：

• #set java environment
     JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-xxxx 这就是刚刚说的那个路径的名称
     JRE_HOME=$JAVA_HOME/jre
     CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
     PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
     export JAVA_HOME JRE_HOME CLASS_PATH PATH
  

  　　
  按shift+: 再按wq!保存退出

• source /etc/profile
  

  echo $JAVA_HOME
  再次查看应该有东西了