//Circle.java
class Circle
{
   //定義程序運行常量π的值
	public static final double PAI = 3.14;
   //定義成員變量：圓的半徑
   public double radius;
   //類的構造函數
   public Circle( double radius)
   {
		this.radius = radius;
   }
   //類的方法成員
   public double getArea()
   {
		return this.radius*this.radius*PAI;
   }
	public static void main(String[] args)
	{
	  Circle aCircle = new Circle( 2.0 );
	  double area = aCircle.getArea();
	  System.out.println("圓的面積是："+ area);
	}
}