1. 使用yum查找jdk: yum search java|grep jdk

   # yum search java|grep jdk
   
   ldapjdk-javadoc.noarch : Javadoc for ldapjdk
   
   java-1.6.-openjdk.x86_64 : OpenJDK Runtime Environment
   
   java-1.6.-openjdk-demo.x86_64 : OpenJDK Demos
   
   java-1.6.-openjdk-devel.x86_64 : OpenJDK Development Environment
   
   java-1.6.-openjdk-javadoc.x86_64 : OpenJDK API Documentation
   
   java-1.6.-openjdk-src.x86_64 : OpenJDK Source Bundle
   
   java-1.7.-openjdk.x86_64 : OpenJDK Runtime Environment
   
   java-1.7.-openjdk-accessibility.x86_64 : OpenJDK accessibility connector
   
   java-1.7.-openjdk-demo.x86_64 : OpenJDK Demos
   
   java-1.7.-openjdk-devel.x86_64 : OpenJDK Development Environment
   
   java-1.7.-openjdk-headless.x86_64 : The OpenJDK runtime environment without
   
   java-1.7.-openjdk-javadoc.noarch : OpenJDK API Documentation
   
   java-1.7.-openjdk-src.x86_64 : OpenJDK Source Bundle
   
   java-1.8.-openjdk.i686 : OpenJDK Runtime Environment
   
   java-1.8.-openjdk.x86_64 : OpenJDK Runtime Environment
   
   java-1.8.-openjdk-accessibility.i686 : OpenJDK accessibility connector
   
   java-1.8.-openjdk-accessibility.x86_64 : OpenJDK accessibility connector
   
   java-1.8.-openjdk-accessibility-debug.i686 : OpenJDK accessibility connector
   
   java-1.8.-openjdk-accessibility-debug.x86_64 : OpenJDK accessibility connector
   
   java-1.8.-openjdk-debug.i686 : OpenJDK Runtime Environment with full debug on
   
   java-1.8.-openjdk-debug.x86_64 : OpenJDK Runtime Environment with full debug on
   
   java-1.8.-openjdk-demo.i686 : OpenJDK Demos
   
   java-1.8.-openjdk-demo.x86_64 : OpenJDK Demos
   
   java-1.8.-openjdk-demo-debug.i686 : OpenJDK Demos with full debug on
   
   java-1.8.-openjdk-demo-debug.x86_64 : OpenJDK Demos with full debug on
   
   java-1.8.-openjdk-devel.i686 : OpenJDK Development Environment
   
   java-1.8.-openjdk-devel.x86_64 : OpenJDK Development Environment
   
   java-1.8.-openjdk-devel-debug.i686 : OpenJDK Development Environment with full
   
   java-1.8.-openjdk-devel-debug.x86_64 : OpenJDK Development Environment with
   
   java-1.8.-openjdk-headless.i686 : OpenJDK Runtime Environment
   
   java-1.8.-openjdk-headless.x86_64 : OpenJDK Runtime Environment
   
   java-1.8.-openjdk-headless-debug.i686 : OpenJDK Runtime Environment with full
   
   java-1.8.-openjdk-headless-debug.x86_64 : OpenJDK Runtime Environment with full
   
   java-1.8.-openjdk-javadoc.noarch : OpenJDK API Documentation
   
   java-1.8.-openjdk-javadoc-debug.noarch : OpenJDK API Documentation for packages
   
   java-1.8.-openjdk-javadoc-zip.noarch : OpenJDK API Documentation compressed in
   
   java-1.8.-openjdk-javadoc-zip-debug.noarch : OpenJDK API Documentation
   
   java-1.8.-openjdk-src.i686 : OpenJDK Source Bundle
   
   java-1.8.-openjdk-src.x86_64 : OpenJDK Source Bundle
   
   java-1.8.-openjdk-src-debug.i686 : OpenJDK Source Bundle for packages with
   
   java-1.8.-openjdk-src-debug.x86_64 : OpenJDK Source Bundle for packages with
   
   java--openjdk.i686 : OpenJDK Runtime Environment
   
   java--openjdk.x86_64 : OpenJDK Runtime Environment
   
   java--openjdk-debug.i686 : OpenJDK Runtime Environment  with full debug on
   
   java--openjdk-debug.x86_64 : OpenJDK Runtime Environment  with full debug on
   
   java--openjdk-demo.i686 : OpenJDK Demos
   
   java--openjdk-demo.x86_64 : OpenJDK Demos
   
   java--openjdk-demo-debug.i686 : OpenJDK Demos  with full debug on
   
   java--openjdk-demo-debug.x86_64 : OpenJDK Demos  with full debug on
   
   java--openjdk-devel.i686 : OpenJDK Development Environment
   
   java--openjdk-devel.x86_64 : OpenJDK Development Environment
   
   java--openjdk-devel-debug.i686 : OpenJDK Development Environment  with full
   
   java--openjdk-devel-debug.x86_64 : OpenJDK Development Environment  with
   
   java--openjdk-headless.i686 : OpenJDK Headless Runtime Environment
   
   java--openjdk-headless.x86_64 : OpenJDK Headless Runtime Environment
   
   java--openjdk-headless-debug.i686 : OpenJDK Runtime Environment with full
   
   java--openjdk-headless-debug.x86_64 : OpenJDK Runtime Environment with full
   
   java--openjdk-javadoc.i686 : OpenJDK  API documentation
   
   java--openjdk-javadoc.x86_64 : OpenJDK  API documentation
   
   java--openjdk-javadoc-debug.i686 : OpenJDK  API documentation for packages
   
   java--openjdk-javadoc-debug.x86_64 : OpenJDK  API documentation for packages
   
   java--openjdk-javadoc-zip.i686 : OpenJDK  API documentation compressed in
   
   java--openjdk-javadoc-zip.x86_64 : OpenJDK  API documentation compressed in
   
   java--openjdk-javadoc-zip-debug.i686 : OpenJDK  API documentation compressed
   
   java--openjdk-javadoc-zip-debug.x86_64 : OpenJDK  API documentation
   
   java--openjdk-jmods.i686 : JMods for OpenJDK
   
   java--openjdk-jmods.x86_64 : JMods for OpenJDK
   
   java--openjdk-jmods-debug.i686 : JMods for OpenJDK  with full debug on
   
   java--openjdk-jmods-debug.x86_64 : JMods for OpenJDK  with full debug on
   
   java--openjdk-src.i686 : OpenJDK Source Bundle
   
   java--openjdk-src.x86_64 : OpenJDK Source Bundle
   
   java--openjdk-src-debug.i686 : OpenJDK Source Bundle for packages with debug
   
   java--openjdk-src-debug.x86_64 : OpenJDK Source Bundle  for packages with
   
   ldapjdk.noarch : The Mozilla LDAP Java SDK

2. 执行安装命令：yum install java-1.8.0-openjdk

   安装成功后，默认安装路径在/usr/lib/jvm/下边，
   如/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.144-0.b01.el6_9.x86_64

   查看安装路径(如下所示)：
   which java
   ls -lrt /usr/bin/java

   [root@preproduct1 ~]# which java
   
   /usr/bin/java
   
   [root@preproduct1 ~]# echo $JAVA_HOME
   
   /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64
   
   [root@preproduct1 ~]# ls -lrt /usr/bin/java
   
   lrwxrwxrwx  root root  Feb  : /usr/bin/java -> /etc/alternatives/java
   
   [root@preproduct1 ~]# ls -lrt /etc/alternatives/java
   
   lrwxrwxrwx  root root  Feb  : /etc/alternatives/java -> /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64/jre/bin/java
   
   [root@preproduct1 ~]# cd /usr/lib/jvm
   
   [root@preproduct1 /usr/lib/jvm]# ll
   
   total
   
   lrwxrwxrwx  root root    Feb  : java -> /etc/alternatives/java_sdk
   
   lrwxrwxrwx  root root    Feb  : java-1.8. -> /etc/alternatives/java_sdk_1.8.0
   
   lrwxrwxrwx  root root    Feb  : java-1.8.-openjdk -> /etc/alternatives/java_sdk_1..0_openjdk
   
   drwxr-xr-x  root root  Feb  : java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64
   
   lrwxrwxrwx  root root    Feb  : java-openjdk -> /etc/alternatives/java_sdk_openjdk
   
   lrwxrwxrwx  root root    Feb  : jre -> /etc/alternatives/jre
   
   lrwxrwxrwx  root root    Feb  : jre-1.8. -> /etc/alternatives/jre_1.8.0
   
   lrwxrwxrwx  root root    Feb  : jre-1.8.-openjdk -> /etc/alternatives/jre_1..0_openjdk
   
   lrwxrwxrwx  root root    Feb  : jre-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64 -> java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64/jre
   
   lrwxrwxrwx  root root    Feb  : jre-openjdk -> /etc/alternatives/jre_openjdk

3. 验证java是否安装成功

   • 查看java版本：java -version

     # java -version
     
     openjdk version "1.8.0_191"
     
     OpenJDK Runtime Environment (build 1.8.0_191-b12)
     
     OpenJDK -Bit Server VM (build 25.191-b12, mixed mode)

   • 查看java是否可用：javac

     # javac
     
     -bash: javac: command not found

     错误原因：默认安装完只有运行环境，java安装目录下只有jre文件夹

4. 安装开发环境yum install java-1.8.0-openjdk-devel.x86_64
   安装完可看到java安装目录下出现bin、lib等文件夹:

   [root@preproduct1 /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64]# l
   
   total
   
   drwxr-xr-x  root root  Feb  : bin
   
   drwxr-xr-x  root root  Feb  : include
   
   drwxr-xr-x  root root  Feb  : jre
   
   drwxr-xr-x  root root  Feb  : lib
   
   drwxr-xr-x  root root  Feb  : tapset

   再次输入javac说明安装成功

   # 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 use
   
     -classpath <path>          Specify where to find user class files and annotationocessors
   
     -cp <path>                 Specify where to find user class files and annotationocessors
   
     -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 compilat is done.
   
     -processor <class1>[,<class2>,<class3>...] Names of the annotation processors ton; 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 imcitly 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 proe
   
     -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

5. 设置环境变量
   修改/etc/profile文件：vi /etc/profile
   在profile文件末尾新增如下内容：

   #set java environment
   
      JAVA_HOME=/usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64
   
      JRE_HOME=$JAVA_HOME/jre
   
      CLASS_PATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JRE_HOME/lib
   
      PATH=$PATH:$JAVA_HOME/bin:$JRE_HOME/bin
   
      export JAVA_HOME JRE_HOME CLASS_PATH PATH

   使环境变量生效：source /etc/profile

   [root@preproduct1 /usr/lib/jvm]# cd /usr/lib/jvm
   
   [root@preproduct1 /usr/lib/jvm]# cd java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64/
   
   [root@preproduct1 /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64]# source /etc/profile
   
   [root@preproduct1 /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64]# echo $JAVA_HOME
   
   /usr/lib/jvm/java-1.8.-openjdk-1.8.0.191.b12-.el7_6.x86_64

至此jdk安装成功