\documentclass{jsarticle}
\usepackage{delarray}
\begin{document}

\begin{displaymath}
\begin{array}({cc})
 a_{11} & a_{12} \\
 a_{21} & a_{22} \\
\end{array}
\end{displaymath}

\begin{displaymath}
f(x) = 
\begin{array}\{{ll}.
 1  & \mathrm{if}\  x > 0. \\
 0  & \mathrm{if}\  x = 0. \\
 -1 & \mathrm{if}\  x < 0. \\
\end{array}
\end{displaymath}

\newcolumntype{L}{>{$}l<{$}}
\begin{displaymath}
 f(x) =
\begin{array}\{{lL}.
 1   & if $x > 0$. \\
 0  & if $x = 0$. \\
 -1 & if $x < 0$. \\
\end{array}
\end{displaymath}

\newcommand\hoge[1][]{\begin{array}[#1] (c) 
  1\\2\\3 \end{array}}
\newcommand\geho[1][]{\left( \begin{array}
 [#1]{c} 1\\2\\3 \end{array}\right)}

\begin{displaymath}
 \hoge[t] \hoge[c] \hoge[b] \neq
 \geho[t] \geho[c] \geho[b]
\end{displaymath}

\end{document}