hello_world.dart

import 'dart:math' as math;



class Circle {
  double _radius;

  Circle({double radius=0.0}){
    this._radius = radius;
  }
 
  //getters
  double get radius=>this._radius;
  double get area => math.pi * math.pow(this._radius, 2);
  //setters
  void set radius(double radius)=>this._radius = radius;
}

void main() {

  var circ1 = Circle(radius:1.23);
  print('Radius before ${circ1.radius}');
   //setter
  circ1.radius = 12;
  print('Radius after: ${circ1.radius}');
   
}