How to refer subfigure with parentheses as Fig.1(a) instead of Fig.1a?

Question

How can I reference the subfigure with this style like Fig.1(a)?
If I use Fig.~\ref{fig_first_case} then I don't get the parentheses.

\documentclass[lettersize,journal]{IEEEtran}
\usepackage{amsmath,amsfonts}
\usepackage[caption=false,font=normalsize,labelfont=sf,textfont=sf]{subfig}
\usepackage{stfloats}
\usepackage{graphicx}
\begin{document}
How can I reference the subfigure with this style like Fig.1(a)?
If I use Fig.~\ref{fig_first_case} then I don't get the parentheses.
\begin{figure}[!t]
\centering
\subfloat[]{\includegraphics[width=2.5in]{example-image-a}%
\label{fig_first_case}}
\hfil
\subfloat[]{\includegraphics[width=2.5in]{example-image-a}%
\label{fig_second_case}}
\caption{Dae. Ad quatur autat ut porepel itemoles dolor autem fuga. Bus quia con nessunti as remo di quatus non perum que nimus. (a) Case I. (b) Case II.}
\label{fig_sim}
\end{figure}
\end{document}

Answer 1

1. Load subfig with labelformat=simple option.
2. Use \renewcommand\thesubfigure{(\alph{subfigure})} in the preamble.

\documentclass[lettersize,journal]{IEEEtran}
\usepackage{amsmath,amsfonts}
\usepackage[caption=false,font=normalsize,labelfont=sf,textfont=sf,labelformat=simple]{subfig}
\usepackage{stfloats}
\usepackage[demo]{graphicx}
\renewcommand\thesubfigure{(\alph{subfigure})}
\begin{document}
    How can I reference the subfigure with this style like Fig.1(a)?
If I use Fig.~\ref{fig_first_case} then I don't get the parentheses. 

\begin{figure*}[!t]
    \centering
    \subfloat[]{\includegraphics[width=2.5in]{example-image-a}%
        \label{fig_first_case}}
    \hfil
    \subfloat[]{\includegraphics[width=2.5in]{example-image-a}%
        \label{fig_second_case}}
    \caption{Dae. Ad quatur autat ut porepel itemoles dolor autem fuga. Bus quia con nessunti as remo di quatus non perum que nimus. (a) Case I. (b) Case II.}
    \label{fig_sim}
\end{figure*}

\end{document}

Only doing step 2 without step 1 will print double parentheses around subfigure labels:

Reference: https://tex.stackexchange.com/a/131366/133968