private void processUsagesPerFile(UsageInfo[] usages) {
    Map<PsiFile, List<EncapsulateFieldUsageInfo>> usagesInFiles =
        new HashMap<PsiFile, List<EncapsulateFieldUsageInfo>>();
    for (UsageInfo usage : usages) {
      PsiElement element = usage.getElement();
      if (element == null) continue;
      final PsiFile file = element.getContainingFile();
      List<EncapsulateFieldUsageInfo> usagesInFile = usagesInFiles.get(file);
      if (usagesInFile == null) {
        usagesInFile = new ArrayList<EncapsulateFieldUsageInfo>();
        usagesInFiles.put(file, usagesInFile);
      }
      usagesInFile.add(((EncapsulateFieldUsageInfo) usage));
    }

    for (List<EncapsulateFieldUsageInfo> usageInfos : usagesInFiles.values()) {
      // this is to avoid elements to become invalid as a result of processUsage
      final EncapsulateFieldUsageInfo[] infos =
          usageInfos.toArray(new EncapsulateFieldUsageInfo[usageInfos.size()]);
      CommonRefactoringUtil.sortDepthFirstRightLeftOrder(infos);

      for (EncapsulateFieldUsageInfo info : infos) {
        EncapsulateFieldHelper helper =
            EncapsulateFieldHelper.getHelper(info.getElement().getLanguage());
        helper.processUsage(
            info,
            myDescriptor,
            myNameToSetter.get(info.getFieldDescriptor().getSetterName()),
            myNameToGetter.get(info.getFieldDescriptor().getGetterName()));
      }
    }
  }