What is the connection between box1 and box4? What happens (memory wise) when both box1 and box4 are declared null?

What is the connection between box1 and box4? What happens (memory wise) when both box1 and box4 are declared null?

Rectangle.java

public class Rectangle

{

public int length;

public int width;

public Rectangle(int l, int w)

{

length = l;

width = w;

}

public Rectangle(int l)

{

this(l, 10);

}

public Rectangle(Rectangle other)

{

this(other.length, other.width);

}

}

Test2.java

public class Test2

{

static int a;

public static void main(String[] args)

{

Rectangle box1 = new Rectangle(10,10);

Rectangle box2 = new Rectangle(box1);

Rectangle box3 = new Rectangle(10);

Rectangle box4 = box1;

box1 = null;

System.out.println("box(l,w) = (" + box2.length + "," + box2.width + ")");

System.out.println("box(l,w) = (" + box3.length + "," + box3.width + ")");

System.out.println("box(l,w) = (" + box4.length + "," + box4.width + ")");

System.out.println("All of the above produce the same output!!!");

box2 = null;

System.out.println("n");

a = 1;

System.out.println("a = " + a);

int a;

a = 101;

System.out.println("a = " + a);

System.out.println("a = " + Test2.a);

}

}