How to install Java in Lenny?

["Edward C. Jones" <edcjones@comcast.net>]

I have a PC with an AMD chip using Lenny (stable), amd64 port.

When I try to run the weather bureau radar loop:

http://radar.weather.gov/radar.php?rid=lwx&product=N0R&overlay=11101111&loop=yes

I get an error message: "Java is necessary for radar looping and is best 
optimized using Java version 1.4.2 or higher." What packages should I 
install so I can use Java?