下面是一个方案：
1.编辑/etc/apt/sources.list文件，将安装源更改为Ubuntu 9.04的安装源为：
deb http://archive.ubuntu.com/ubuntu/ jaunty main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ jaunty-security main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ jaunty-proposed main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu/ jaunty-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ jaunty main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ jaunty-security main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ jaunty-updates main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu/ jaunty-proposed main restricted universe multiverse

2. sudo apt-get install sun-java5-jdk

3. 接下来的工作是,配置JRE环境:
在shell执行:
sudo update-alternatives --config java
通常会给出两个或两个以上选择的路径
选择：/usr/lib/jvm/java-1.5.0-sun/jre/bin/java作为你的JRE

4.建议安装安装浏览器Java插件(不是必要的)：
在shell中执行:
sudo apt-get install sun-java5-plugin

以上