public static List<String> toRelativeFiles(@NotNull VirtualFile root,@NotNull final Collection<VirtualFile> files){
  ArrayList<String> rc=new ArrayList<String>(files.size());
  for (  VirtualFile file : files) {
    rc.add(relativePath(root,file));
  }
  return rc;
}

public static List < String > toRelativeFiles ( @ NotNull VirtualFile root , @ NotNull final Collection < VirtualFile > files ) { ArrayList < String > rc = new ArrayList < String > ( files . size ( ) ) ; for ( VirtualFile file : files ) { rc . add ( relativePath ( root , file ) ) ; } return rc ; }
covert list of files to relative paths
