#java# 新系统安装Java Development Kit

直接下载jdk压缩包方式安装

　分为下面5个步骤

   1.官网下载JDK

   2.解压缩,放到指定目录

   3.配置环境变量

   4.设置系统默认JDK

　5. 测试jdk

1.官网下载JDK　　　

     地址: http://www.oracle.com/technetwork/articles/javase/index-jsp-138363.html

　　选择相应的 .gz包下载 

2. 解压缩,放到指定目录(以jdk-8u101-linux-x64.tar.gz为例)

　　创建目录:

sudo mkdir /usr/lib/jvm

　加压缩到该目录:

 sudo tar -zxvf jdk-8u101-linux-x64.tar.gz -C /usr/lib/jvm

3.修改环境变量:　　

sudo vim ~/.bashrc

　文件的末尾追加下面内容:

#set oracle jdk environment
export JAVA_HOME=/usr/lib/jvm/jdk1.8.0_101  ## 这里要注意目录要换成自己解压的jdk 目录

export JRE_HOME=${JAVA_HOME}/jre  

export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib  

export PATH=${JAVA_HOME}/bin:$PATH  

　使环境变量马上生效

 source ~/.bashrc

4.设置系统默认jdk 版本

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8.0_101/bin/java 300  

sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8.0_101/bin/javac 300  

sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8.0_101/bin/jar 300   

sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.8.0_101/bin/javah 300   

sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.8.0_101/bin/javap 300   

　然后执行:

sudo update-alternatives --config java

    若是初次安装jdk,会有下面的提示     

   There is only one alternative in link group java (providing /usr/bin/java): 
    /usr/lib/jvm/jdk1.8.0_101/bin/java

　否者,选择合适的jdk

5.测试jdk

java -version

java version "1.8.0_101"

Java(TM) SE Runtime Environment (build 1.8.0_101-b13)

Java HotSpot(TM) 64-Bit Server VM (build 25.101-b13, mixed mode)

  jdk 安装成功

from: 

http://www.cnblogs.com/a2211009/p/4265225.html