定义一个抽象类shape,它包含一个抽象方法getArea(),从Shape类派生除Rectangle和Circle类，这两个类都用getArea()方法计算对象的面积。编写应用程序使用Rectangle和Circle类。
代码如下：
abstract class Shape {
abstract double getArea();
}
class Rectangle extends Shape{
double Hight;
double Wide;
public Rectangle(double hight, double wide) {
Hight = hight;
Wide = wide;
}
@Override
double getArea() {
return Hight*Wide/2;
}
}
class Circle extends Shape{
int Radius;
public Circle(int radius) {
Radius = radius;
}
@Override
double getArea() {
return Radius*Radius* Math.PI;
}
}
测试类：
public class ShapeTest {
public static void main(String[] args) {
Rectangle rectangle=new Rectangle(6,6);
Circle circle=new Circle(5);
System.out.println("矩形面积="+rectangle.getArea());
System.out.println("圆形面积="+circle.getArea());
}
}