Linux Centos7 卸载JDK1.7 并安装JDK1.8

1.准备好需要的jdk安装包
2.查看系统自带jdk
[root@localhost ~]# rpm -qa|grep jdk
java-1.7.0-openjdk-headless-1.7.0.51-2.4.5.5.el7.x86_64
java-1.7.0-openjdk-1.7.0.51-2.4.5.5.el7.x86_64
3.删除系统自带jdk
[root@localhost ~]# rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.51-2.4.5.5.el7.x86_64
[root@localhost ~]# rpm -e --nodeps java-1.7.0-openjdk-1.7.0.51-2.4.5.5.el7.x86_64

4.在/user/目录下创建java目录
[root@localhost ~]# mkdir /usr/java 
[root@localhost ~]# cd /usr/java 

5.将下载好的JDK安装包，传入/usr/java目录，然后解压
[root@localhost java]# tar -zxvf jdk-8u181-linux-x64.tar.gz

6.设置环境变量
[root@localhost java]# vi /etc/profile

#set java environment
export JAVA_HOME=/usr/java/jdk1.8.0_181
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH

让修改生效
[root@localhost java]# source /etc/profile

7.验证JDK有效性
[root@localhost java]# java -version
java version "1.8.0_181"
Java(TM) SE Runtime Environment (build 1.8.0_181-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.181-b13, mixed mode)