下载JDK

jre-7u75-linux-x64.tar.gz,下载地址：http://www.oracle.com/technetwork/java/javase/downloads/jdk7-downloads-1880260.html

解压JDK包

tar -zxvf jre-7u75-linux-x64.tar.gz

mv jre1.7.0_75 /usr/java/

完成后配置JAVA环境变量

vim /root/.bash_profile

增加如下环境变量：

JAVA_HOME=/usr/java/jre1.7.0_75

export JRE_HOME=/usr/java/jre1.7.0_75

export PATH=$PATH:/usr/java/jre1.7.0_75/bin

export CLASSPATH=./:/usr/java/jre1.7.0_75/lib

export JAVA_HOME

然后生效配置文件

source /root/.bash_profile

正常情况下是可以java -version查看当前java版本了。如果系统之前有JDK的话，那还要执行一下命令

sudo update-alternatives --install /usr/bin/java java /usr/java/jre1.7.0_75/bin/java 300

sudo update-alternatives --install /usr/bin/javac javac /usr/java/jre1.7.0_75/javac 300

sudo update-alternatives --config java

There is 1 program that provides 'java'.

Selection Command

-----------------------------------------------

*+ 1 /usr/java/jre1.7.0_75/bin/java

Enter to keep the current selection[+],or type selection number: 1

java -version

java version "1.7.0_75"

Java(TM) SE Runtime Environment (build 1.7.0_75-b13)

Java HotSpot(TM) 64-Bit Server VM (build 24.75-b04,mixed mode)

这样JDK就安装好了。