circle.java

java2应用开发指南第一版

//Circle.java
public class Circle
{
   //定义程序运行常量π的值
	public static final double PAI = 3.14;
   //定义成员变量：圆的半径
   public static double radius;
   //类的构造函数
   public Circle( double radius)
   {
		Circle.radius = radius;
   }
   //类的方法成员
   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("圆的面积是："+ area);
		System.exit(0);
	}
}