[root@baidu1 ~]# java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-b08)
OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)
[root@baidu1 ~]# whereis java
java: /usr/bin/java /usr/lib/java /etc/java /usr/share/java /usr/share/man/man1/java.
[root@baidu1 ~]# ls -l /usr/bin/java
lrwxrwxrwx. 1 root root 22 Aug 13 15:12 /usr/bin/java -> /etc/alternatives/java
[root@baidu1 ~]# ls -l /etc/alternatives/java
lrwxrwxrwx. 1 root root 71 Aug 13 15:12 /etc/alternatives/java -> /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-1.el7.x86_64/jre/bin/java
[root@baidu1 ~]# cd /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.242.b08-1.el7.x86_64/jre/bin
[root@baidu1 bin]# ll
total 232
-rwxr-xr-x. 1 root root 8680 Apr 3 00:14 java
-rwxr-xr-x. 1 root root 8800 Apr 3 00:14 jjs
-rwxr-xr-x. 1 root root 8800 Apr 3 00:14 keytool
-rwxr-xr-x. 1 root root 8872 Apr 3 00:14 orbd
-rwxr-xr-x. 1 root root 8800 Apr 3 00:14 pack200
-rwxr-xr-x. 1 root root 8808 Apr 3 00:14 policytool
-rwxr-xr-x. 1 root root 8800 Apr 3 00:14 rmid
-rwxr-xr-x. 1 root root 8808 Apr 3 00:14 rmiregistry
-rwxr-xr-x. 1 root root 8808 Apr 3 00:14 servertool
-rwxr-xr-x. 1 root root 8872 Apr 3 00:14 tnameserv
-rwxr-xr-x. 1 root root 113800 Apr 3 00:14 unpack200
[root@baidu1 bin]# ./java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-b08)
OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)查找可用的jdk rpm
yum -y list Java*
安装用到版本：
yum install java-1.6.0-openjdk.x86_64
升级java版本：
rpm -qa| grep java
卸载搜索到的软件:
rpm -e --nodeps <搜索到包>
配置PATH
vi /etc/profile