1.首先，检查已安装的jdk版本

sudo yum list installed | grep java

2.移除、卸载圈红的系统自带的openjdk

sudo yum remove java-1.7.0-openjdk.x86_64
sudo yum remove java-1.7.0-openjdk-headless.x86_64
sudo yum remove java-1.8.0-openjdk.x86_64
sudo yum remove java-1.8.0-openjdk-headless.x86_64

3.配置环境变量并使其生效
1) 编辑/etc/profile

vi /etc/profile

添加如下内容：

export JAVA_HOME=/usr/java/jdk-14.0.2
export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export PATH=$PATH:$JAVA_HOME/bin

2) 使/etc/profile生效

source /etc/profile

4.查看oracle jdk是否配置成功

java -version