Rust メソッド構文(Java説明用)

Main.java

class Circle {
  private double radius;
  Circle(double radius){
    this.radius = radius;
  }
  public double area(){
    return Math.PI * (this.radius * this.radius);
  }
}

class Main {
  public static void main(String[] args){
    Circle c = new Circle(2.0);
    System.out.println("area is " + c.area());
  }
}