class Circle4_2
{
	//Ա
	private final double PI=3.1415926;	//Բ
	private double radius;				//Բ뾶˽гԱ		
	//Ա
	public double area()				//Բ
	{
		return PI*radius*radius;
	}		
	public void setRadius(double r)		//Բ뾶ֵд
	{		
		radius=r;
	}	
	//mainJavaӦóڵ
	public static void main(String[] args)
	{	
		//ʹĬϹ췽
		Circle4_2 c=new Circle4_2();
		c.setRadius(10);		
		System.out.println("뾶Ϊ10ԲΪ"+c.area());
	}
}
