查看CentOS自带JDK是否已安装

[root@test ~]# yum list installed |grep java

若有自带安装的JDK，应如下操作进行卸载CentOS系统自带Java环境

[root@test ~]# java -version
java version "1.7.0_181"
OpenJDK Runtime Environment (rhel-2.6.14.8.el6_9-x86_64 u181-b00)
OpenJDK 64-Bit Server VM (build 24.181-b00, mixed mode)

[root@test ~]# yum -y remove java-1.7.0-openjdk*
[root@test ~]# yum -y remove tzdata-java.noarch

[root@test ~]# java --version
-bash: /usr/bin/java: No such file or directory

查看yum库中的Java安装包

[root@test ~]# yum -y list java*
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: centos.ustc.edu.cn
* extras: centos.ustc.edu.cn
* updates: centos.ustc.edu.cn
base | 3.7 kB 00:00 
extras | 3.4 kB 00:00 
updates | 3.4 kB 00:00 
Available Packages
java-1.5.0-gcj.x86_64 1.5.0.0-29.1.el6 base 
java-1.5.0-gcj-devel.x86_64 1.5.0.0-29.1.el6 base 
java-1.5.0-gcj-javadoc.x86_64 1.5.0.0-29.1.el6 base 
java-1.5.0-gcj-src.x86_64 1.5.0.0-29.1.el6 base 
java-1.6.0-openjdk.x86_64 1:1.6.0.40-1.13.12.6.el6_8 updates
java-1.6.0-openjdk-demo.x86_64 1:1.6.0.40-1.13.12.6.el6_8 updates
java-1.6.0-openjdk-devel.x86_64 1:1.6.0.40-1.13.12.6.el6_8 updates
java-1.6.0-openjdk-javadoc.x86_64 1:1.6.0.40-1.13.12.6.el6_8 updates
java-1.6.0-openjdk-src.x86_64 1:1.6.0.40-1.13.12.6.el6_8 updates
java-1.7.0-openjdk.x86_64 1:1.7.0.111-2.6.7.2.el6_8 updates
java-1.7.0-openjdk-demo.x86_64 1:1.7.0.111-2.6.7.2.el6_8 updates
java-1.7.0-openjdk-devel.x86_64 1:1.7.0.111-2.6.7.2.el6_8 updates
java-1.7.0-openjdk-javadoc.noarch 1:1.7.0.111-2.6.7.2.el6_8 updates
java-1.7.0-openjdk-src.x86_64 1:1.7.0.111-2.6.7.2.el6_8 updates
java-1.8.0-openjdk.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-debug.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-demo.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-demo-debug.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-devel.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-devel-debug.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-headless.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-headless-debug.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-javadoc.noarch 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-javadoc-debug.noarch 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-src.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java-1.8.0-openjdk-src-debug.x86_64 1:1.8.0.101-3.b13.el6_8 updates
java_cup.x86_64 1:0.10k-5.el6 base 
java_cup-javadoc.x86_64 1:0.10k-5.el6 base 
java_cup-manual.x86_64 1:0.10k-5.el6 base 
javacc.x86_64 4.1-0.5.el6 base 
javacc-demo.x86_64 4.1-0.5.el6 base 
javacc-manual.x86_64 4.1-0.5.el6 base 
javassist.noarch 3.9.0-6.el6 base 
javassist-javadoc.noarch 3.9.0-6.el6 base

以yum库中java-1.8.0为例, "*"表示将java-1.8.0的所有相关Java程序都安装上

[root@test ~]# yum -y install java-1.8.0-openjdk*

查看刚安装的Java版本信息。

输入："java -version" 可查看Java版本

输入："javac" 可查看Java的编译器命令用法

*************** 当你发现自己的才华撑不起野心时，就请安静下来学习吧！***************