code: public static BugCollection combineBugHistories() {
          try {
              FBFileChooser chooser = new FBFileChooser();
              chooser.setFileFilter(new FindBugsAnalysisFileFilter());
              // chooser.setCurrentDirectory(GUISaveState.getInstance().getStarterDirectoryForLoadBugs());
              // This is done by FBFileChooser.
              chooser.setMultiSelectionEnabled(true);
              chooser.setDialogTitle(edu.umd.cs.findbugs.L10N.getLocalString("dlg.choose_xmls_ttl", "Choose All XML's To Combine"));
              if (chooser.showOpenDialog(MainFrame.getInstance()) == JFileChooser.CANCEL_OPTION) {
                  return null;
              }
  
              SortedBugCollection conglomeration = new SortedBugCollection();
              conglomeration.readXML(chooser.getSelectedFiles()[0]);
              Update update = new Update();
              for (int x = 1; x < chooser.getSelectedFiles().length; x++) {
                  File f = chooser.getSelectedFiles()[x];
                  SortedBugCollection col = new SortedBugCollection();
                  col.readXML(f);
                  conglomeration = (SortedBugCollection) update.mergeCollections(conglomeration, col, false, false);// False
                  // means
                  // dont
                  // show
                  // dead
                  // bugs
              }
  
              return conglomeration;
          } catch (IOException e) {
              Debug.println(e);
              return null;
          } catch (DocumentException e) {
              Debug.println(e);
              return null;
          }
  
      }
docs: TODO: This really needs to be rewritten such that they don't have to
  choose ALL xmls in one fel swoop. I'm thinking something more like new
  project wizard's functionality. -Dan
  
  Merges bug collection histories from xmls selected by the user. Right now
  all xmls must be in the same folder and he must select all of them at
  once Makes use of FindBugs's mergeCollection method in the Update class
  of the workflow package
  
  @return the merged collecction of bugs