2.5  Example: Definition of the class Circle

/*
+-------------+      +-------+
| Circle      |  +-->| Posn  |
+-------------+  |   +-------+
| Posn center |--+   | int x |
| int radius  |      | int y |
+-------------+      +-------+
*/

// to represent a circle
class Circle {
  Posn center;
  int radius;

  Circle(Posn center, int radius) {
    this.center = center;
    this.radius = radius;
  }
}

/* Intreractions:
Examples of the use of the constructor for the class Circle

Circle c1 = new Circle(new Posn(10, 20), 10);
Circle c2 = new Circle(new Posn(20, 40), 15);

Examples of the use of the field selectors for the class Circle

c1.center         -- expected: new Posn(10, 20)
c1.radius         -- expected: 10

c2.center         -- expected: new Posn(20, 40)
c2.radius         -- expected: 15

c1.center.x       -- expected 10
c1.center.y       -- expected 20
c2.center.x       -- expected 20
c2.center.y       -- expected 40
*/