本文摘自CSDN，原文地址：https://blog.csdn.net/music0ant/article/details/89818633，侵删。

1. 检查系统中的jdk版本

java -version

显示：

openjdk version "1.8.0_102"

OpenJDK Runtime Environment (build 1.8.0_102-b14)

OpenJDK 64-Bit Server VM (build 25.102-b14, mixed mode)

2. 查询自带的openjdk

rpm -qa | grep -i java

显示：

java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64

java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64

java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64

java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64

3. 卸载openjdk

rpm -e --nodeps java-1.7.0-openjdk-1.7.0.111-2.6.7.8.el7.x86_64

rpm -e --nodeps java-1.7.0-openjdk-headless-1.7.0.111-2.6.7.8.el7.x86_64

rpm -e --nodeps java-1.8.0-openjdk-1.8.0.102-4.b14.el7.x86_64

rpm -e --nodeps java-1.8.0-openjdk-headless-1.8.0.102-4.b14.el7.x86_64

或者使用

yum remove *openjdk*

之后再次输入rpm -qa | grep java查看卸载情况

4. 检查系统环境

uname -a

Linux localhost.localdomain 3.10.0-327.el7.x86_64 #1 SMP Thu Nov 19 22:10:57 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

5. 下载

https://www.oracle.com/technetwork/java/javase/downloads/jdk8-downloads-2133151.html

解压

mkdir -p /usr/local/java

tar zxvf /var/local/jdk-8u211-linux-x64.tar.gz -C /usr/local/java

6. 配置环境变量

vim /etc/profile

注：如果修改当前用户的环境变量编辑~/.profile或~/.bashrc文件即可，而不是/etc/profile。

在文件最后添加如下配置：

JAVA_HOME=/usr/local/java/jdk1.8.0_211

export CLASSPATH=$:CLASSPATH:$JAVA_HOME/lib/

export PATH=$PATH:$JAVA_HOME/bin

重新加载配置文件，使配置生效(su root)：

source /etc/profile

或

source ~/.bash_profile

7. 检查是否安装成功

查看java安装脚本

java -version

显示：

java version "1.8.0_211"
Java(TM) SE Runtime Environment (build 1.8.0_211-b12)
Java HotSpot(TM) 64-Bit Server VM (build 25.211-b12, mixed mode)

查看执行参数

javac

Usage: javac <options> <source files>
where possible options include:
-g Generate all debugging info
-g:none Generate no debugging info
-g:{lines,vars,source} Generate only some debugging info
-nowarn Generate no warnings
-verbose Output messages about what the compiler is doing
-deprecation Output source locations where deprecated APIs are used
-classpath <path> Specify where to find user class files and annotation processors
-cp <path> Specify where to find user class files and annotation processors
-sourcepath <path> Specify where to find input source files
-bootclasspath <path> Override location of bootstrap class files
-extdirs <dirs> Override location of installed extensions
-endorseddirs <dirs> Override location of endorsed standards path
-proc:{none,only} Control whether annotation processing and/or compilation is done.
-processor <class1>[,<class2>,<class3>...] Names of the annotation processors to run; bypasses default discovery process
-processorpath <path> Specify where to find annotation processors
-parameters Generate metadata for reflection on method parameters
-d <directory> Specify where to place generated class files
-s <directory> Specify where to place generated source files
-h <directory> Specify where to place generated native header files
-implicit:{none,class} Specify whether or not to generate class files for implicitly referenced files
-encoding <encoding> Specify character encoding used by source files
-source <release> Provide source compatibility with specified release
-target <release> Generate class files for specific VM version
-profile <profile> Check that API used is available in the specified profile
-version Version information
-help Print a synopsis of standard options
-Akey[=value] Options to pass to annotation processors
-X Print a synopsis of nonstandard options
-J<flag> Pass <flag> directly to the runtime system
-Werror Terminate compilation if warnings occur
@<filename> Read options and filenames from file