Complete the code:

public class Test

$\{$

public static void main$($String $[]$ args$)$

$\{$

int $i=4$; int $j=5_{{?}_{?}}$

$//$ Fill in the code to invoke the sum method and display the sum of i and $j.$

public static int sum$($int $i,$ int $j)$

$\{$

$//$ Fill in the code here to return the sum of i and $j.$

$\}$

$\}$