CentOS 7 安装 jdk1.8

1. 解压jdk包：

[root@localhost ~]# tar -zxvf jdk-8u161-linux-x64.tar.gz -C /opt/

2. 修改jdk文件夹名（方便记忆）：

[root@ruijie packages]# cd /opt/
[root@ruijie opt]$ mv jdk1.8.0_161/ jdk8

3.配置jdk环境变量：

[root@ruijie jdk8]# vi /etc/profile

#set jdk environment
export JAVA_HOME=/opt/jdk8/
export JRE_HOME=/opt/jdk8/jre
export PATH=$PATH:$JAVA_HOME/bin
export PATH=$PATH:$JRE_HOME/bin

4. 重新读取/etc/profile配置文件

[root@ruijie ~]# source /etc/profile

5. 验证环境变量是否配置成功：

[root@ruijie ~]# 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)

[root@ruijie ~]# 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

6. OK!!!