Are objects cleaned up when references to them are nulled?

Question

public class App1 
{

 public static void main(String[] args) 
 {
   Point point_1 = new Point(5,5);
   Point point_2 = new Point(7,8);
   Circle circle_1 = new Circle(point_2, 10);
   point_1 = null;
   point_2 = null;
 }
}

How many object references exist after this code has executed? Why?

Answer 1

After this code has executed, exactly none, since it will have exited :-)

If you mean at the point just before exit, there's a reference on the stack to your circle and a reference in your circle to the second point, assuming the constructor stores it.