ubuntu12.10安装jdk1.7

1、去官网下载JDK

http://www.oracle.com/technetwork/java/javase/downloads/index.html

2、root权限并解压，复制到/usr/lib/jvm

sudo su

tar -zxvf jdk-7u21-linux-i586.tar.gz
mv jdk1.7.0_21/ /usr/lib/jvm
3、配置环境变量

gedit ~/.bashrc

在末尾添加

export JAVA_HOME=/usr/lib/jvm/jdk1.7.0_21
export JRE_HOME=${JAVA_HOME}/jre
export CLASSPATH=.:${JAVA_HOME}/lib:${JRE_HOME}/lib
export PATH=${JAVA_HOME}/bin:$PATH

立即生效：source ~/.bashrc
4、配置默认JDK

sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.7.0_21/bin/java 300 
sudo update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.7.0_21/bin/javac 300 
sudo update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.7.0_21/bin/jar 300

检查

sudo update-alternatives --config java 

5、查看java版本号

命令行：

java -version

java 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)