Using the code I already have

I need help figuring out how to write the diag$2$ for a magic square in JAVA. This is the code I have so far.

import java.util.$*$;

import java.io$.*$;

public class Main $\{$

static Scanner inp $=$ new Scanner$($System$.$in$)$;

private int$[][]$ square;

private boolean$[]$ possible;

private int totalSqs;

private int magicConst;

private int numsquares;

public Main$($int N$)\{$

if $($N $<=2)\{$

System.out.print$("$Only give values $>2!!")$;

System.exit$(1)$;

$\}$

square $=$ new int $[$N$][$N$]$; $//$ initialize with zeros by default

magicConst $=$ this.findMagicConstant$($N$)$;

totalSqs $=$ N$*$N;

possible $=$ new boolean$[$totalSqs$]$;

for$($int i $=0$; i $<$ totalSqs; i $++)$

possible$[$i$]=$ true;

numsquares $=0$;

$\}$

public int findMagicConstant$($int N$)\{$

int last$\_$num $=$ N$*$N;

int sum $=$ last$\_$num $*($last$\_$num $+1)/2$;

return sum$/$N;

$\}$

public void fill$($int row, int col$)\{$

if $($validSquare$())\{$

System.out.println$("$Done$!!")$;

for$($int$[]$ rws: square$)\{$

System.out.println$($Arrays$.$toString$($rws$))$;

$\}$

$\}$

if $($row $==$ square.length$)\{$

$//$System$.$out.println$($this$)$;

numsquares$++$;

return;

$\}$

$//$System$.$out.println$($totalSqs$)$;

for$($int i $=0$; i