centos yum 安装 jdk1.8

JDK:

版本：1.8
服务器默认安装1.7，所以不使用默认安装

yum -y list java*   --查看yum的jdk安装包

yum  install  java-1.8.0-openjdk   java-1.8.0-openjdk-devel --安装JDK,如果没有java-1.8.0-openjdk-devel就没有javac命令 
也可用 yum install java-1.8.0-openjdk* 安装所有java1.8.0所有Java程序

配置环境变量

通过yum默认安装的路径为 /usr/lib/jvm

/usr/lib/jvm

ls -la

total 24
drwxr-xr-x   4 root root  4096 Oct 16 17:19 .
dr-xr-xr-x. 45 root root 12288 Oct 16 17:19 ..
lrwxrwxrwx   1 root root    26 Oct 16 17:19 java -> /etc/alternatives/java_sdk
lrwxrwxrwx   1 root root    32 Oct 16 17:19 java-1.8.0 -> /etc/alternatives/java_sdk_1.8.0
lrwxrwxrwx   1 root root    40 Oct 16 17:19 java-1.8.0-openjdk -> /etc/alternatives/java_sdk_1.8.0_openjdk
drwxr-xr-x   9 root root  4096 Oct 16 17:20 java-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64
drwxr-xr-x   9 root root  4096 Oct 16 17:20 java-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64-debug
lrwxrwxrwx   1 root root    34 Oct 16 17:19 java-openjdk -> /etc/alternatives/java_sdk_openjdk
lrwxrwxrwx   1 root root    21 Oct 16 17:19 jre -> /etc/alternatives/jre
lrwxrwxrwx   1 root root    27 Oct 16 17:19 jre-1.8.0 -> /etc/alternatives/jre_1.8.0
lrwxrwxrwx   1 root root    35 Oct 16 17:19 jre-1.8.0-openjdk -> /etc/alternatives/jre_1.8.0_openjdk
lrwxrwxrwx   1 root root    51 Oct 16 17:19 jre-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64 -> java-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64/jre
lrwxrwxrwx   1 root root    57 Oct 16 17:19 jre-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64-debug -> java-1.8.0-openjdk-1.8.0.144-0.b01.el7_4.x86_64-debug/jre
lrwxrwxrwx   1 root root    29 Oct 16 17:19 jre-openjdk -> /etc/alternatives/jre_openjdk

进入java的文件夹下发现bin目录，JAVA_HOME指向一个含有java可执行程序的目录(一般是在 bin/java中,此目录为/bin/java的上级目录)
让系统上的所有用户使用java(openjdk),则配置/etc/profile
vi /etc/profile
在文件最后加入如下行

JAVA_HOME=/usr/lib/jvm/java
PATH=$PATH:$JAVA_HOME/bin
CLASSPATH=.:$JAVA_HOME/lib/dt.jar:$JAVA_HOME/lib/tools.jar
export JAVA_HOME CLASSPATH PATH

验证
java -version
javac -version
jdk1.8安装成功