problems installing java

[Brett Wiggins]

hi,
   I am using FreeBSD 5.2.1 -RELEASE as a desktop and have come across some problems when installing java. I downloaded the files listed in the handbook into /usr/ports/distfiles/ and went to install /usr/ports/java/jdk13 with 'make install clean'. The installation starts 
then stops saying that i need to download a diablo caffe file and place it in /usr/ports/distfiles/. I download the file, start the install again and get the following;

# Start of jdk build
i386 Build started:   1.3.1-p8-root-040913-23:10
ERROR: Your BOOTDIR environment variable does not point
       to a valid Java 2 SDK for bootstrapping this build.
       A Java 2 SDK 1.3.1 build must be bootstrapped against any
       1.3 build. Please update your ALT_BOOTDIR setting, or
       just unset it, and start your build again.
 
Exiting because of the above error(s).
gmake: *** [sanity] Error 1
*** Error code 2
 
Stop in /usr/ports/java/jdk13.

What does this error message mean? I have all the files that were listed in /usr/ports/distfiles what am I missing or doing wrong?

thanks

Brett