I want someone to explain when to use ++x, --x, ++y, --y in for loop with examples and codes.

Secondly, look at this code :

class Uber{

static int y = 2;

Uber(int x) {this(); y = y*2;}

Uber() {y++; }

}

class Minor extends Uber{

Minor() {super(y); y = y+3; }

public static void main (

String[] args) {

new Minor();

System.out.println(y);

}}

The answer given in the book of Kathy and Bert is 9.But, i think the answer should be 7. Because,y = 2 and y*2 is 4. With increment of 3 plus 4 i.e y+3(3+4) =7