What is the runtime complexity $($Big$-$O$)$ of the pow$()$

method shown below?

Answer.

public static long pow$($ long x$,$ int n $)\{$

if $($n $==0)$

return $1$;

if $($n $==1)$

return x;

if $($isEven$($n$))$

return pow$($x$*$x$,$ n$/2)$;

else

return pow$($x$*$x$,$ n$/2)*$ x;

$\}$

public static boolean isEven$($int n$)\{$

return $($n$\%2==0)$