安装完Ubuntu8.1之后，如果想要开发或运行Java程序，就需要安装JDK或JRE。下面就介绍一种最为简便的在Ubuntu中安装JDK的方法。
众所周知，Sun公司对于Linux下的的JDK安装控制是相当严格：（1）预编译成二进制的JDK包是需要取得Sun公司授权的；（2）Sun公司有自己的Unix操作系统。或许是因为这两点原因，目前在Linux或Unix系统中安装JDK要比Windows中安装JDK复杂许多。通常许多安装方法都是需要先去Sun公司的Java页面上下载JDK包，再编译安装。
在Ubuntu中，安装JDK也有很多方法。下面介绍一种比较简单的方法：
（1）使用apt-get命令安装：
sudo apt-get install sun-java6-jdk
如果能够很顺利安装完成。那么恭喜你，运气不错。但是，你很有可能会遇到如下错误：“E: Couldn't find package sun-java6-jdk”。那么你需要首先更新apt-get的源，换句话说，就是更新软件的版本信息。在更新之前，最好修改一下/etc/apt/sources.list，因为如果是在国内上网的Ubuntu，总是去连接国外的服务器，会比较慢。可以先备份原来的sources.list:
sudo cp /etc/apt/sources.list /etc/apt/sources.list.bak
然后修改sources.list：
sudo gedit /etc/apt/sources.list
将下面内容覆盖原有内容：
#中国* *大学更新服务器
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-updates main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-backports main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-security main restricted universe multiverse
deb http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://ubuntu.csie.ntu.edu.tw/ubuntu/ hardy-proposed main restricted universe multiverse#*官方更新源
deb http://tw.archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb http://tw.archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-security main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-updates main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-backports main restricted universe multiverse
deb-src http://tw.archive.ubuntu.com/ubuntu hardy-proposed main restricted universe multiverse
#Ubuntu.cn99.com更新服务器
deb http://ubuntu.cn99.com/ubuntu/ hardy main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-security main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-updates main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb http://ubuntu.cn99.com/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb-src http://ubuntu.cn99.com/ubuntu/ hardy-backports main restricted universe multiverse
#Ubuntu 官方源(欧洲)
deb http://archive.ubuntu.com/ubuntu/ hardy main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ hardy-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ hardy-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ hardy-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ hardy main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ hardy-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ hardy-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ hardy-proposed main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ hardy-backports main restricted universe multiverse
#中国科学技术大学更新服务器（教育网，推荐校园网和网通用户使用）：
deb http://debian.ustc.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb http://debian.ustc.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb-src http://debian.ustc.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
#Mirror.lupaworld.com更新服务器（浙江省杭州市双线服务器）：
deb http://mirror.lupaworld.com/ubuntu hardy main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-security main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-updates main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-backports main restricted universe multiverse
deb http://mirror.lupaworld.com/ubuntu hardy-proposed main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-security main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-updates main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-backports main restricted universe multiverse
deb-src http://mirror.lupaworld.com/ubuntu hardy-proposed main restricted universe multiverse
#厦门大学更新服务器（教育网服务器）：
deb ftp://ubuntu.realss.cn/ubuntu/ hardy main restricted universe multiverse
deb ftp://ubuntu.realss.cn/ubuntu/ hardy-backports restricted universe multiverse
deb ftp://ubuntu.realss.cn/ubuntu/ hardy-proposed main restricted universe multiverse
deb ftp://ubuntu.realss.cn/ubuntu/ hardy-security main restricted universe multiverse
deb ftp://ubuntu.realss.cn/ubuntu/ hardy-updates main restricted universe multiverse
deb-src ftp://ubuntu.realss.cn/ubuntu/ hardy main restricted universe multiverse
deb-src ftp://ubuntu.realss.cn/ubuntu/ hardy-backports main restricted universe multiverse
deb-src ftp://ubuntu.realss.cn/ubuntu/ hardy-proposed main restricted universe multiverse
deb-src ftp://ubuntu.realss.cn/ubuntu/ hardy-security main restricted universe multiverse
deb-src ftp://ubuntu.realss.cn/ubuntu/ hardy-updates main restricted universe multiverse
#成都市 电子科技大学更新服务器（教育网，推荐校园网和网通用户使用）：
deb http://ubuntu.uestc.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb http://ubuntu.uestc.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb http://ubuntu.uestc.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb http://ubuntu.uestc.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb http://ubuntu.uestc.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb-src http://ubuntu.uestc.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
#如果无法解析uestc.edu.cn域名，请使用以下地址
deb http://ubuntu.dormforce.net/ubuntu/ hardy main multiverse restricted universe
deb http://ubuntu.dormforce.net/ubuntu/ hardy-backports main multiverse restricted universe
deb http://ubuntu.dormforce.net/ubuntu/ hardy-proposed main multiverse restricted universe
deb http://ubuntu.dormforce.net/ubuntu/ hardy-security main multiverse restricted universe
deb http://ubuntu.dormforce.net/ubuntu/ hardy-updates main multiverse restricted universe
deb-src http://ubuntu.dormforce.net/ubuntu/ hardy main multiverse restricted universe
deb-src http://ubuntu.dormforce.net/ubuntu/ hardy-backports main multiverse restricted universe
deb-src http://ubuntu.dormforce.net/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://ubuntu.dormforce.net/ubuntu/ hardy-security main multiverse restricted universe
deb-src http://ubuntu.dormforce.net/ubuntu/ hardy-updates main multiverse restricted universe
#上海市上海交通大学更新服务器（教育网，推荐校园网和网通用户使用）：
deb http://ftp.sjtu.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb http://ftp.sjtu.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ hardy main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ hardy-backports main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ hardy-security main multiverse restricted universe
deb-src http://ftp.sjtu.edu.cn/ubuntu/ hardy-updates main multiverse restricted universe
#北京市清华大学更新服务器（教育网，推荐校园网和网通用户使用）：
deb http://mirror9.net9.org/ubuntu/ hardy main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ hardy-backports main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ hardy-proposed main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ hardy-security main multiverse restricted universe
deb http://mirror9.net9.org/ubuntu/ hardy-updates main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ hardy main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ hardy-backports main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ hardy-security main multiverse restricted universe
deb-src http://mirror9.net9.org/ubuntu/ hardy-updates main multiverse restricted universe
#沈阳市东北大学更新服务器（教育网，推荐校园网和网通用户使用）：
deb ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy main multiverse restricted universe
deb ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-backports main multiverse restricted universe
deb ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-proposed main multiverse restricted universe
deb ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-security main multiverse restricted universe
deb ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-updates main multiverse restricted universe
deb-src ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy main multiverse restricted universe
deb-src ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-backports main multiverse restricted universe
deb-src ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-proposed main multiverse restricted universe
deb-src ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-security main multiverse restricted universe
deb-src ftp://ftp.neu.edu.cn/mirror/archive.ubuntu.com/ubuntu/ hardy-updates main multiverse restricted universe
接下来，执行apt-get的更新过程:
sudo apt-get update
程序将分析/etc/apt/sources.list，自动连网寻找list中对应的Packages/Sources/Release列表文件，如果有更新则下载之，存入/var/lib/apt/lists/目录。
如果你的网速比较快，那么这个过程应该很快就能够完成。
接下来，就可以再重新运行jdk安装命令：
sudo apt-get install sun-java6-jdk
（2）设置默认的java程序的版本：
sudo update-alternatives --config java
按照提示输入对应的选项，指定为JDK 6
（3）设置Java环境变量：
sudo vim /etc/environment
在其中添加如下两行：
CLASSPATH=/usr/lib/jvm/java-6-sun/lib
JAVA_HOME=/usr/lib/jvm/java-6-sun
如果其中已经设置了CLASSPATH和JAVA_HOME，则将其修改为上面的形式，保存退出。
如此，Ubuntu中的JDK就已经安装完成了。其实，如果第一步的命令没有出错，那么安装的过程将更加迅速便捷。即使有第一步命令遇到安装错误，那么通过修改souces.list，速度应该也是比较快的。最重要的是，这种安装方法相对于源码安装，或者是将jdk.bin编译成deb再安装的方法而言，还是比较容易一些的。
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