1、下载jdk安装包

jdk下载地址：https://www.oracle.com/java/technologies/downloads/

Oracle 登录账号：2028056560@qq.com
Oracle 登录密码：Oracle1234
若是不行，可以尝试在Oracle登录密码和账号中找一个，链接：https://bugmenot.com/view/oracle.com

2、在centos7 创建文件夹

此文件夹随便起名，我这里创建一个app文件夹，并将下载好的jdk安装文件放到此文件夹下

cd /
mkdir /app/java

3、解压jdk文件

tar -zxvf jdk-8u401-linux-x64.tar.gz

4、配置环境变量

a、打开环境变量文件

vim /etc/profile

b、将配置信息复制进去。

注意：JAVA_HOME=/app/java/jdk1.8.0_401，/app/java/jdk1.8.0_401替换成你实际上安装地址

export JAVA_HOME=/app/java/jdk1.8.0_401export CLASSPATH=.:$JAVA_HOME/jre/lib/rt.jar:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jarexport PATH=$PATH:$JAVA_HOME/bin

c、重新加载环境变量

source /etc/profile

5、测试是否成功

java -version

输出

[root@test ~]# java -version
java version "1.8.0_401"
Java(TM) SE Runtime Environment (build 1.8.0_401-b10)
Java HotSpot(TM) 64-Bit Server VM (build 25.401-b10, mixed mode)
[root@test ~]# 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[root@test ~]# java
Usage: java [-options] class [args...](to execute a class)or  java [-options] -jar jarfile [args...](to execute a jar file)
where options include:-d32	  use a 32-bit data model if available-d64	  use a 64-bit data model if available-server	  to select the "server" VMThe default VM is server,because you are running on a server-class machine.-cp <class search path of directories and zip/jar files>-classpath <class search path of directories and zip/jar files>A : separated list of directories, JAR archives,and ZIP archives to search for class files.-D<name>=<value>set a system property-verbose:[class|gc|jni]enable verbose output-version      print product version and exit-version:<value>Warning: this feature is deprecated and will be removedin a future release.require the specified version to run-showversion  print product version and continue-jre-restrict-search | -no-jre-restrict-searchWarning: this feature is deprecated and will be removedin a future release.include/exclude user private JREs in the version search-? -help      print this help message-X            print help on non-standard options-ea[:<packagename>...|:<classname>]-enableassertions[:<packagename>...|:<classname>]enable assertions with specified granularity-da[:<packagename>...|:<classname>]-disableassertions[:<packagename>...|:<classname>]disable assertions with specified granularity-esa | -enablesystemassertionsenable system assertions-dsa | -disablesystemassertionsdisable system assertions-agentlib:<libname>[=<options>]load native agent library <libname>, e.g. -agentlib:hprofsee also, -agentlib:jdwp=help and -agentlib:hprof=help-agentpath:<pathname>[=<options>]load native agent library by full pathname-javaagent:<jarpath>[=<options>]load Java programming language agent, see java.lang.instrument-splash:<imagepath>show splash screen with specified image
See http://www.oracle.com/technetwork/java/javase/documentation/index.html for more details.