//Circle.java
public 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 static double radius;
   //類的構造函數
   public Circle( double radius)
   {
		Circle.radius = radius;
   }
   //類的方法成員
   public static double getArea()
   {
		return radius*radius*PAI;
   }
	public static void main(String[] args)
	{
		Circle aCircle = new Circle( 2.0 );
		double area = Circle.getArea();
		System.out.println("圓的面積是："+ area);
		System.exit(0);
	}
}