swap elements of diagonal
for ( int i = 0 ; i < N ; ++ i ) if ( i != N / 2 ) { int temp = array [ i ] [ i ] ; array [ i ] [ i ] = array [ i ] [ N - i - 1 ] ; array [ i ] [ N - i - 1 ] = temp ; } for ( int i = 0 ; i < N ; ++ i ) { for ( int j = 0 ; j < N ; ++ j ) System . out . print ( array [ i ] [ j ] + " ▁ " ) ; System . out . println ( ) ; } }