GetBlueJ
From WikiEducator
Obtaining the BlueJ software
Go to the [BlueJ website] and click the download link. From here you can select the version you need for your operating system.
Double click (or drag to the applications folder) the downloaded file to install BlueJ (see the installation Instructions for further detailed information.
After it is installed you have an option to read the readme file and/or launch BlueJ itself.