CentOS 7 安装成功后可能已经默认安装了OpenJDK的JRE，但平时进行java开发时需要用完整的JDK，所以为了避免以后不必要的麻烦，在此卸载了OpenJDK的JRE，并重新安装了Oracle的JDK8
1.安装说明
系统环境：CentOS 7
安装方式：rpm
安装包：jdk-8u131-linux-x64.rpm
2.检查系统原安装版本
[hadoop@centos7-1 ~]$ java -version
OpenJDK Version "1.8.0_131"
OpenJDK Runtime Environment (build 1.8.0_131-b12)
OpenJDK 64-Bit Server VM (build 25.131-b12, mixed mode)
[hadoop@centos7-1 ~]$ rpm -qa|grep java
libvirt-java-devel-0.4.9-4.el7.noarch
tzdata-java-2017b-1.el7.noarch
java-1.8.0-openjdk-headless-1.8.0.131-3.b12.el7_3.x86_64
java-1.7.0-openjdk-1.7.0.141-2.6.10.1.el7_3.x86_64
libvirt-java-0.4.9-4.el7.noarch
javapackages-tools-3.4.1-11.el7.noarch
java-1.7.0-openjdk-headless-1.7.0.141-2.6.10.1.el7_3.x86_64
java-1.8.0-openjdk-1.8.0.131-3.b12.el7_3.x86_64
python-javapackages-3.4.1-11.el7.noarch
[hadoop@centos7-1 ~]$ 3.卸载系统已安装的openjdk
libvirt-java-devel-0.4.9-4.el7.noarch
libvirt-java-0.4.9-4.el7.noarch
tzdata-java-2017b-1.el7.noarch
java-1.8.0-openjdk-headless-1.8.0.131-3.b12.el7_3.x86_64
java-1.7.0-openjdk-1.7.0.141-2.6.10.1.el7_3.x86_64
java-1.7.0-openjdk-headless-1.7.0.141-2.6.10.1.el7_3.x86_64
java-1.8.0-openjdk-1.8.0.131-3.b12.el7_3.x86_64以root身份运行以下命令
[root@centos7-1 hadoop]# rpm -e --nodeps libvirt-java-devel-0.4.9-4.el7.noarch
[root@centos7-1 hadoop]# rpm -e --nodeps libvirt-java-0.4.9-4.el7.noarch
[root@centos7-1 hadoop]# rpm -e --nodeps tzdata-java-2017b-1.el7.noarch
[root@centos7-1 hadoop]# rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.141-2.6.10.1.el7_3.x86_64
[root@centos7-1 hadoop]# rpm -e --nodeps java-1.7.0-openjdk-1.7.0.141-2.6.10.1.el7_3.x86_64
[root@centos7-1 hadoop]# rpm -e --nodeps java-1.8.0-openjdk-headless-1.8.0.131-3.b12.el7_3.x86_64
[root@centos7-1 hadoop]# rpm -e --nodeps java-1.8.0-openjdk-1.8.0.131-3.b12.el7_3.x86_644.安装jdk
[root@centos7-1 local]# ll /usr/local/jdk-8u131-linux-x64.rpm
-rw-r--r--. 1 root root 169983496 6月 12 23:17 /usr/local/jdk-8u131-linux-x64.rpm
[root@centos7-1 local]# rpm -ivh jdk-8u131-linux-x64.rpm
Preparing... ################################# [100%]
Updating / installing...
1:jdk1.8.0_131-2000:1.8.0_131-fcs ################################# [100%]
Unpacking JAR files...
tools.jar...
plugin.jar...
javaws.jar...
deploy.jar...
rt.jar...
jsse.jar...
charsets.jar...
localedata.jar...
[root@centos7-1 local]# jdk默认安装到了 /usr/java/ 下面
[root@centos7-1 local]# ll /usr/java/
total 0
lrwxrwxrwx. 1 root root 16 6月 12 23:18 default -> /usr/java/latest
drwxr-xr-x. 9 root root 268 6月 12 23:18 jdk1.8.0_131
lrwxrwxrwx. 1 root root 22 6月 12 23:18 latest -> /usr/java/jdk1.8.0_131
[root@centos7-1 local]# 5.验证安装
[root@centos7-1 local]# ll /usr/bin/java
lrwxrwxrwx. 1 root root 22 6月 12 23:18 /usr/bin/java -> /etc/alternatives/java
[root@centos7-1 local]# ll /etc/alternatives/java
lrwxrwxrwx. 1 root root 35 6月 12 23:18 /etc/alternatives/java -> /usr/java/jdk1.8.0_131/jre/bin/java
[root@centos7-1 local]# java -version
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)
[root@centos7-1 local]# 6.配置环境变量
[hadoop@centos7-1 ~]$ whoami
hadoop
[hadoop@centos7-1 ~]$ vi ~/.bashrc设置JAVA_HOME，并将它加到PATH中
JAVA_HOME=/usr/java/default
PATH=$PATH:$JAVA_HOME/bin
export JAVA_HOME PATH运行source命令，使修改生效。输出JAVA_HOME, PATH确认修改是否生效。
[hadoop@centos7-1 ~]$ source ~/.bashrc
[hadoop@centos7-1 ~]$ echo $JAVA_HOME
/usr/java/default
[hadoop@centos7-1 ~]$ echo $PATH
/usr/lib64/qt-3.3/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/usr/sbin:/bin:/sbin:/home/hadoop/.local/bin:/home/hadoop/bin:/usr/java/default/bin至此，CentOS 7上安装JDK8顺利完毕，更多关于linux下安装JDK的文章请查看下面相关链接
