How can I add numbers to specific equations in an eqnarray*?

Question

I know how to use \nonumber or \notag in \begin{eqnarray} \end{eqnarray} environment.

But is there something like \addnumber or \addtag in \begin{eqnarray*} \end{eqnarray*} environment ?

For example, if I want only the second equation below be tagged, what should I do?

\begin{eqnarray*}
a &=& b\\ 
c &=& d  \addnumber\\ 
e &=& f\\
g &=& h\\
i &=& j
\end{eqnarray*} 

Answer 1

\documentclass {article}
\usepackage{amsmath}
\newcommand\addtag{\refstepcounter{equation}\tag{\theequation}}

\begin{document}

\begin{align*}
a &= b\\ 
c &= d  \addtag \\ 
e &= f\\
g &= h\\
i &= j
\end{align*}

\end{document}