private static boolean containsOnlyPrivates(final PsiClass aClass) {
    final PsiField[] fields = aClass.getFields();
    for (PsiField field : fields) {
      if (!field.hasModifierProperty(PsiModifier.PRIVATE)) return false;
    }

    final PsiMethod[] methods = aClass.getMethods();
    for (PsiMethod method : methods) {
      if (!method.hasModifierProperty(PsiModifier.PRIVATE)) {
        if (method.isConstructor()) { // skip non-private constructors with call to super only
          final PsiCodeBlock body = method.getBody();
          if (body != null) {
            final PsiStatement[] statements = body.getStatements();
            if (statements.length == 0) continue;
            if (statements.length == 1 && statements[0] instanceof PsiExpressionStatement) {
              final PsiExpression expression =
                  ((PsiExpressionStatement) statements[0]).getExpression();
              if (expression instanceof PsiMethodCallExpression) {
                PsiReferenceExpression methodExpression =
                    ((PsiMethodCallExpression) expression).getMethodExpression();
                if (methodExpression.getText().equals(PsiKeyword.SUPER)) {
                  continue;
                }
              }
            }
          }
        }
        return false;
      }
    }

    final PsiClass[] inners = aClass.getInnerClasses();
    for (PsiClass inner : inners) {
      if (!inner.hasModifierProperty(PsiModifier.PRIVATE)) return false;
    }

    return true;
  }
  public Collection<String> findConflicts(
      @NotNull final PsiElement element, @NotNull final PsiElement[] allElementsToDelete) {
    if (element instanceof PsiMethod) {
      final PsiClass containingClass = ((PsiMethod) element).getContainingClass();

      if (containingClass != null && !containingClass.hasModifierProperty(PsiModifier.ABSTRACT)) {
        final PsiMethod[] superMethods = ((PsiMethod) element).findSuperMethods();
        for (PsiMethod superMethod : superMethods) {
          if (isInside(superMethod, allElementsToDelete)) continue;
          if (superMethod.hasModifierProperty(PsiModifier.ABSTRACT)) {
            String message =
                RefactoringBundle.message(
                    "0.implements.1",
                    RefactoringUIUtil.getDescription(element, true),
                    RefactoringUIUtil.getDescription(superMethod, true));
            return Collections.singletonList(message);
          }
        }
      }
    } else if (element instanceof PsiParameter) {
      final PsiElement scope = ((PsiParameter) element).getDeclarationScope();
      if (scope instanceof PsiMethod) {
        final PsiMethod method = (PsiMethod) scope;
        final PsiClass containingClass = method.getContainingClass();
        if (containingClass != null) {
          final int parameterIndex =
              method.getParameterList().getParameterIndex((PsiParameter) element);
          final PsiMethod methodCopy = (PsiMethod) method.copy();
          methodCopy.getParameterList().getParameters()[parameterIndex].delete();
          final MultiMap<PsiElement, String> conflicts = new MultiMap<>();
          ConflictsUtil.checkMethodConflicts(containingClass, method, methodCopy, conflicts);
          return (Collection<String>) conflicts.values();
        }
      }
    }
    return null;
  }