系統(tǒng)版本

[root@localhost ~]# cat /etc/redhat-release CentOS Linux release 7.4.1708 (Core)

#安裝之前先查看一下有無系統(tǒng)自帶jdk

rpm -qa |grep javarpm -qa |grep jdkrpm -qa |grep gcj

#如果有就使用批量卸載命令

rpm -qa | grep java | xargs rpm -e --nodeps

?

直接yum安裝1.8.0版本openjdk

[root@localhost ~]# yum install java-1.8.0-openjdk* -y

查看版本

[root@localhost ~]# java -version openjdk version "1.8.0_161" OpenJDK Runtime Environment (build 1.8.0_161-b14) OpenJDK 64-Bit Server VM (build 25.161-b14, mixed mode)

默認(rèn)jre jdk 安裝路徑是/usr/lib/jvm 下面

?

JAVA_HOME指向一個(gè)含有java可執(zhí)行程序的目錄(一般是在?bin/java中,此目錄為/bin/java的上級(jí)目錄),用cd 命令進(jìn)入到 jvm下唯一的一個(gè)目錄中?java-1.8.0-openjdk-1.8.0.161-0.b14.el7_3.x86_64,發(fā)現(xiàn)其下目錄為?

/jar/bin/java.jre-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64?這個(gè)鏈接是指向?java-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64/jre 這個(gè)文件夾，所以，可以直接用export命令將 JAVA_HOME 指向

?jre-1.8.0-openjdk-1.8.0.121-0.b14.el7_4.x86_64這個(gè)鏈接.

?

#臨時(shí)生效

[root@localhost ~]# export JAVA_HOME=/usr/lib/jvm/<span style="font-family: Arial;">jre-1.8.0-openjdk-1.8.0.121-0.b13.el7_3.x86_64</span>

#當(dāng)前用戶生效的配置

vim ~/.bashrc #在文件底部加入下面一句 export JAVA_HOME=/usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64

#如果使所有用戶生效的配置

vim /etc/profile

?#set?java?environment??

export JAVA_HOME=/usr/lib/jvm/javaexport CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/jre/lib/rt.jarexport PATH=$PATH:$JAVA_HOME/bin

?

#使得配置生效

. /etc/profile

?

#查看變量

[root@localhost ~]# echo $JAVA_HOME /usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64

?[root@localhost ~]# echo $CLASSPATH
.:/usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64/lib/dt.jar:/usr/lib/jvm/jre-1.8.0-openjdk-1.8.0.161-0.b14.el7_4.x86_64/lib/tools.jar

?javac 和java 命令都有輸出設(shè)置提示就表示安裝和環(huán)境配置成功了

案例如下：

[root@instanc]#?yum -y list java??

Loaded plugins: langpacks, versionlock

Error: No matching Packages to list

[root@instanc]#?rpm -qa |grep java

[root@instanc]#?rpm -qa |grep jdk

[root@instanc]#?rpm -qa |grep gcj

[root@instanc]#?yum install java-1.8.0-openjdk* -y

--------中間有安裝過程，最后complete

Complete!

[root@instance-ozyu8y37 ~]#?java -version

openjdk version "1.8.0_191"

OpenJDK Runtime Environment (build 1.8.0_191-b12)

OpenJDK 64-Bit Server VM (build 25.191-b12, mixed mode)

[root@instance-ozyu8y37 ~]#?cd /usr

[root@instance-ozyu8y37 usr]# ls

bin? etc? games? include? lib? lib64? libexec? local? sbin? share? src? tmp

[root@instance-ozyu8y37 usr]#?cd lib

[root@instance-ozyu8y37 lib]#?cd jvm

[root@instance-ozyu8y37 jvm]# ls

java

java-1.8.0

java-1.8.0-openjdk

java-1.8.0-openjdk-1.8.0.191.b12-0.el7_5.x86_64

java-1.8.0-openjdk-1.8.0.191.b12-0.el7_5.x86_64-debug

java-openjdk

jre

jre-1.8.0

jre-1.8.0-openjdk

jre-1.8.0-openjdk-1.8.0.191.b12-0.el7_5.x86_64

jre-1.8.0-openjdk-1.8.0.191.b12-0.el7_5.x86_64-debug

jre-openjdk

[root@instance-ozyu8y37 jvm]#?vim /etc/profile? ?# 配置java環(huán)境變量（所有用戶）

# System wide environment and startup programs, for login setup

# Functions and aliases go in /etc/bashrc

?

# It's NOT a good idea to change this file unless you know what you

# are doing. It's much better to create a custom.sh shell script in

# /etc/profile.d/ to make custom changes to your environment, as this

# will prevent the need for merging in future updates.

?

pathmunge () {

? ? case ":${PATH}:" in

? ? ? ? *:"$1":*)

? ? ? ? ? ? ;;

? ? ? ? *)

? ? ? ? ? ? if [ "$2" = "after" ] ; then

? ? ? ? ? ? ? ? PATH=$PATH:$1

? ? ? ? ? ? else

? ? ? ? ? ? ? ? PATH=$1:$PATH

? ? ? ? ? ? fi

? ? esac

}

?

?

if [ -x /usr/bin/id ]; then

? ? if [ -z "$EUID" ]; then

? ? ? ? # ksh workaround

? ? ? ? EUID=`/usr/bin/id -u`

? ? ? ? UID=`/usr/bin/id -ru`

? ? fi

? ? USER="`/usr/bin/id -un`"

? ? LOGNAME=$USER

? ? MAIL="/var/spool/mail/$USER"

fi

#set java environment??

?

export JAVA_HOME=/usr/lib/jvm/java

?

export CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar:$JAVA_HOME/jre/lib/rt.jar

?

export PATH=$PATH:$JAVA_HOME/

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