Install JDK on CentOS 7

1. Download oracle jdk Download address: http://www.oracle.com/technetwork/java/javase/downloads/index.html Select the same protocol and download jdk in rpm format, or jdk in tar.gz format.

2. Uninstall the native openjdk

2.1、查询本机jdk信息

    rpm -qa|grep jdk
    java-1.7.0-openjdk-headless-1.7.0.171-2.6.13.0.el7_4.x86_64
    copy-jdk-configs-2.2-5.el7_4.noarch
    java-1.7.0-openjdk-1.7.0.171-2.6.13.0.el7_4.x86_64
    java-1.8.0-openjdk-headless-1.8.0.161-0.b14.el7_4.x86_64
    java-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64

2.2、使用rpm -e --nodeps命令卸载jdk

     rpm -e --nodeps  java-1.7.0-openjdk-headless-1.7.0.171-2.6.13.0.el7_4.x86_64
     rpm -e --nodeps  copy-jdk-configs-2.2-5.el7_4.noarch
     rpm -e --nodeps   java-1.7.0-openjdk-1.7.0.171-2.6.13.0.el7_4.x86_64
     rpm -e --nodeps   java-1.8.0-openjdk-headless-1.8.0.161-0.b14.el7_4.x86_64
     rpm -e --nodeps   java-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64

3. Install jdk

3.1、安装rpm格式jdk
    进入安装文件目录，执行

        [root@ou Downloads]# rpm -ivh jdk-8u161-linux-x64.rpm

    默认安装到usr/java。
3.2、安装tar.gz格式jdk
    进入安装文件目录，执行
    tar -xzvf jdk-8u161-linux-x64.tar.gz  -C /usr/java

4. Modify environment variables

4.1、打开/etc/profile
```
[root@ou etc]# cd /etc
[root@ou etc]# geidt profile
```
4.2、在最后添加
```
JAVA_HOME=/usr/java/jdk1.8.0_161
JRE_HOME=/usr/java/jdk1.8.0_161/jre
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar  
PATH=$JAVA_HOME/bin:$JRE_HOME/bin:$PATH  
export JAVA_HOME CLASSPATH PATH JRE_HOME
```
4.3、重新加载profile文件
保存文件后，执行
```
[root@ou etc]# source /etc/profile
```

5. Test the java version

```
[root@ou etc]# java -version
java version "1.8.0_161"
Java(TM) SE Runtime Environment (build 1.8.0_161-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.161-b12, mixed mode)
```

Install JDK on CentOS 7

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