通过程序设计几何图形(Shape)、矩形(Rectangle)、圆形(Circle)、正方形(Square)几种类型,
能够利用接口和多态性计算几何图形的面积和周长并显示。
interface Shape {//声明接口Shape
final
float PI = 3.14f; // 定义常量圆周率
abstract
void area();//定义抽象方法面积
abstract
void perimeter();//定义抽象方法周长
}
class bian {
double
width;// 定义变量宽
double
length;// 定义变量长
double
radius; // 定义变量半径
double
S;// 定义变量面积
double
C;// 定义变量周长
public bian(double width, double length, double radius) {
this.width
= width;
this.length
= length;
this.radius
= radius;
}
}
class Rectangle extends bian implements Shape {//实现接口
public
Rectangle(double width, double length, double radius) {
super(width,
length, radius);
}
public void area() {
S
= width * length;
System.out.println("矩形面积:"
+ S);// 输出
}
public void perimeter() {
C
= (width + length) * 2;
System.out.println("矩形周长:"
+ C);// 输出
}
}
class Circle extends bian implements Shape {//实现接口
public
Circle(double width, double length, double radius) {
super(width,
length, radius);
}
public void area() {
S
= PI * radius * radius;
System.out.println("圆形面积:"
+ S);// 输出
}
public void perimeter() {
C
= 2 * PI * radius;
System.out.println("圆形周长:"
+ C);// 输出
}
}
class Square extends bian implements Shape {//实现接口
public
Square(double width, double length, double radius) {
super(width,
length, radius);
}
public void area() {
S
= width * width;
System.out.println("正方形面积:"
+ S);// 输出
}
public void perimeter() {
C
= (width + width) * 2;
System.out.println("正方形周长:"
+ C);// 输出
}
}
public class jiekoutuxing {
public static void main(String[] args) {
Shape
p1;//声明接口变量
p1
= new Rectangle(4.0, 5.0, 0);//实现类对象赋值接口变量
p1.area();//接口回调
p1.perimeter();//接口回调
p1 = new Circle(0, 0, 2.0);//实现类对象赋值接口变量
p1.area();
p1.perimeter();
p1 = new Square(3.0, 0, 0);//实现类对象赋值接口变量
p1.area();
p1.perimeter();
}
}