The VJProjects collection contains all of the VJProjects in the solution.
You can access just the collection of Visual J++ projects with DTE.VJProjects.
Remarks
The Visual J++ package defines a VJProjects collection that is immediately accessible from the DTE Object, and this collection contains a project object for each Visual J++ project in the solution.
There is no projects collection containing all projects in the solution. The Solution object contains all the projects in the solution.