用面向对象的思想定义一个接口Area，其中包含一个计算面积的方法CalsulateArea()，然后设计MyCircle和MyRectangle两个类都实现这个接口中的方法CalsulateArea()，分别计算圆和矩形的面积，最后写出测试以上类和方法的程序

接口Area：
public interface Area {
double calsulateArea();
}MyCircle：
public class MyCircle implements Area {
private double radius;

public MyCircle(double radius) {
this.radius = radius;
}

@Override
public double calsulateArea() {
return Math.PI * radius * radius;
}
}MyRectangle：
public class MyRectangle implements Area {
private double length;
private double width;

public MyRectangle(double length, double width) {
this.length = length;
this.width = width;
}

@Override
public double calsulateArea() {
return length * width;
}
}测试程序：
public class Test {
public static void main(String[] args) {
Area circle = new MyCircle(5);
Area rectangle = new MyRectangle(5, 6);
System.out.println("圆的面积为：" + circle.calsulateArea());
System.out.println("矩形的面积为：" + rectangle.calsulateArea());
}
}