The Java SDK for Macintosh version 1.4.2 and the NetBeans IDE for Macintosh must be downloaded and installed separately. There is no combined download package for this combination of Java version and NetBeans IDE.
Downloading the Java software
Go to the Apple - Support - Downloads - Java Update 1.4.2 Update 2 download page and click on the "Download" link. After clicking on the link, the download should begin automatically. This download is approximately 26 Megabytes in size.
Downloading the NetBeans software
Go to the NetBeans IDE 5.0 Download page and click on the "Mac OS X" link in the NetBeans IDE 5.0 Download Installers table. The download should begin automatically.
Installing the NetBeans Software
After downloading the software bundle, the installation instructions for this package can be found on the NetBeans Community web site here (you must scroll down to see the Macintosh installation instructions).