private @Nullable ProblemDescriptor getStringBuilderToStringProblem(final @NotNull PsiMethodCallExpression call) {
      final ProblemDescriptor descriptor = getRedundantStringBuilderToStringProblem(call);
      if (descriptor != null) return descriptor;
      return getUseContentEqualsProblem(call);
    }
private @Nullable ProblemDescriptor getStringBuilderToStringProblem(final @NotNull PsiMethodCallExpression call)