CentOS替换系统自带JDK

1.解压jdk安装包到/opt 下

/opt/jdk1.8.0_181

2.编辑/etc/profile， 增加如下内容

export JAVA_HOME=/opt/jdk1.8.0_181
export CLASSPATH=.:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/lib/dt.jar
export PATH=$PATH:${JAVA_HOME}/bin

3.执行命令

source /etc/profile

4.执行下面命令更新jdk，最后输入数字选择正确的jdk版本

update-alternatives --install /usr/bin/java java /opt/jdk1.8.0_181/bin/java 300
update-alternatives --install /usr/bin/javac javac /opt/jdk1.8.0_181/bin/javac 300
update-alternatives --install /usr/bin/jar jar /opt/jdk1.8.0_181/bin/jar 300
update-alternatives --config java