1、到 Sun 的官网下载选择 accept license ，然后选择适合自己机型的JDK下载。2、解压文件，修改文件名3、添加环境变量加入如下内容4、配置默认JDK版本然后执行若是初次安装 JDK， 将提示若是非初次安装，将有不同版本的 JDK 选项。5、测试
$ sudo mkdir /usr/lib/jvm$ sudo tar zxvf jdk-7u21-linux-i586.tar.gz -C /usr/lib/jvm$ cd /usr/lib/jvm$ sudo mv jdk1.7.0_21 java
$ sudo vim ~/.bashrc
export JAVA_HOME=/usr/lib/jvm/javaexport JRE_HOME=${JAVA_HOME}/jreexport CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/libexport PATH=${JAVA_HOME}/bin:$PATHsudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/java/bin/java 300sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/java/bin/javac 300sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/java/bin/jar 300sudo update-alternatives --install /usr/bin/javah javah /usr/lib/jvm/java/bin/javah 300sudo update-alternatives --install /usr/bin/javap javap /usr/lib/jvm/java/bin/javap 300
sudo update-alternatives --config java
There is only one alternative in link group java (providing /usr/bin/java): /usr/lib/jvm/java/bin/java无需配置。
$ java -versionjava version "1.7.0_21"Java(TM) SE Runtime Environment (build 1.7.0_21-b11)Java HotSpot(TM) Server VM (build 23.21-b01, mixed mode)