What is the change in oxidation number of carbon in the following reaction ?

${\mathrm{CH}}_4\left(\mathrm{g}\right)+4{\mathrm{Cl}}_2\left(\mathrm{g}\right)\to {\mathrm{CCl}}_4\left(\mathrm{l}\right)+4\mathrm{HCl}\left(\mathrm{g}\right)$

$\stackrel{-4}{\mathrm{C}}{\mathrm{H}}_4+4\stackrel{\circ }{\mathrm{C}}{\mathrm{I}}_2\to \stackrel{+4}{\mathrm{C}}{{\mathrm{Cl}}_4}_{\left(\mathrm{l}\right)}+4\mathrm{H}\stackrel{-1}{{\mathrm{Cl}}_{\left(\mathrm{g}\right)}}$

$\begin{array}{l}x+4=0\hspace{0.25em} \hspace{0.25em}\hspace{0.25em}\hspace{0.25em}x-4(-1)=0\\ x=-4\hspace{0.25em}\hspace{0.25em}\hspace{0.25em}\hspace{0.25em} x=+4\end{array}$

In the above reaction, carbon oxidation number is changed from –4 to +4.