The Java JDK and NetBeans Integrated Development Environment (IDE) are provided by Sun Microsystems as a combined package that requires only one download with an installer that installs both products at the same time.
Go to the Sun Developer Network NetBeans bundle download page (link provided below) and click on the "Download" link. This will take you to the Download page that lists the platforms this package is available for. Before you can proceed with the download you must click on the "Accept License Agreement" radio button. Then you can click on the download link for the Linux package (which is the first entry in the list). After clicking on the link, the download should begin automatically. This download is approximately 115 Megabytes and may take a while to download.
Here is the link: Download J2SE Development Kit 5.0 Update 10 with NetBeans IDE 5.5 Bundle
Installing the Software
After downloading the software bundle, the installation instructions for this package can be found on the Sun Developer Network here. Note that the installation requires 415 Megabytes of free space (235 Mbytes permanent space and 180 Mbytes temporary space, and that you will need to accept the license agreement again during the installation process.