Opened Files Browser mode displays a convenient list of pointers to files that are frequently accessed. These files are not necessarily part of the project, though they are kept with the project. For example, when you select Build|Make or Build|Rebuild, the files in the project are compiled, not the files in the Opened Files Browser.
Click the left-arrow icon above the Opened Files list to return to the previous group of working set files.
See also:
Getting Started with JBuilder: AppBrowser modes