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://download.oracle.com/otn-pub/java/jdk/8u181-b13/96a7b8442fe848ef90c96a2fad6ed6d1/jdk-8u181-linux-x64.tar.gz

2. 解压缩,放到指定目录(以jdk-7u60-linux-x64.gz为例)

创建目录:

sudo mkdir /usr/lib/jvm

加压缩到该目录:

 sudo tar -zxvf jdk-7u60-linux-x64.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/jdk1.7.0_60  ## 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/jdk1.7.0_60/bin/java 300  
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_60/bin/javac 300  
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_60/bin/jar 300   
sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/jdk1.7.0_60/bin/javah 300   
sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/jdk1.7.0_60/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/jdk1.7.0_60/bin/java

否者,选择合适的jdk

5.测试jdk

java -version

显示

java version "1.7.0_60"
Java(TM) SE Runtime Environment (build 1.7.0_60-b19)
Java HotSpot(TM) 64-Bit Server VM (build 24.60-b09, mixed mode)?

jdk安装成功

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cs