Yes, my feeling would be to add a visitor pattern to the ReadOnlyVFS:

// General acceptance visitor
Iterator<VirtualFile> scan(Visitor acceptVisitor);
// Simple visitor wrapper that would use a simple VirtualFile name regex
Iterator<VirtualFile> scan(String fileNameRegex);

Why? The vfs uses the getChildren call to traverse the files. The jar is handled by a vf impl. Show me why a jar needs to be treated as a seperate url protocol.

The following scan method has been added:

public interface ReadOnlyVFS
{
 /**
 * Scan the VFS for files accepted by the visitor.
 *
 * @param acceptVisitor - the visitor that defines which files to accept
 * @return Iterator<VirtualFile> of the matches
 */
 public Iterator<VirtualFile> scan(VFSVisitor acceptVisitor);
}

public interface VFSVisitor
{
 /**
 * Visit a virtual file and indicate if it should be included in the scan.
 * A directory must be included if its children are to be scanned.
 * @param vf - the virtual file to test for inclusion
 * @return true if the file should be included.
 */
 public boolean visit(VirtualFile vf);
}

When do you need to know whether a file is a jar or not from an external use point of view?