题目： 设计一个形状类(接口)Shape,方法:求周长和求面积形状类(接口)的子类(实现类);:Rect(矩形),Circle(圆形)Rect类的子类:Square(正方形)不同的子类会有不同的计算周长和面积的方法。 创建三个不同的形状对象,放在Shape类型的数组里,分别打印出每个对象的周长和面积。
形状接口
public interface Shape {// 求面积方法double getArea();// 求周长方法double getPerimeter();}圆形类
public class Circle implements Shape {private final double PI = 3.14; //圆周率private double r; //半径public double getR() {return r;}public void setR(double r) {this.r = r;}public Circle(double r) {this.r = r;}@Overridepublic double getArea() {// TODO Auto-generated method stubreturn PI * r * r;}@Overridepublic double getPerimeter() {// TODO Auto-generated method stubreturn PI * r * 2;}}矩形类
public class Rect implements Shape {private double width; // 宽private double height; // 高public double getWidth() {return width;}public void setWidth(double width) {this.width = width;}public double getHeight() {return height;}public void setHeight(double height) {this.height = height;}// 一个参数构造，给子类正方形用public Rect(double width) {this.width = width;}//两个参数的构造，自己用public Rect(double width, double height) {this.height = height;this.width = width;}@Overridepublic double getArea() {// TODO Auto-generated method stubreturn width * height;}@Overridepublic double getPerimeter() {// TODO Auto-generated method stubreturn 2 * (width + height);}}正方形，继承矩形
public class Square extends Rect {public Square(double width) {super(width);}@Overridepublic double getArea() {// TODO Auto-generated method stubreturn getWidth() * getWidth();}@Overridepublic double getPerimeter() {// TODO Auto-generated method stubreturn 4 * getWidth();}}测试类
public class Test {public static void main(String[] args) {Shape[] shape = new Shape[3];shape[0] = new Circle(3);System.out.println("========圆形周长和面积========");System.out.println(String.format("%.2f", shape[0].getArea()));System.out.println(shape[0].getPerimeter());shape[1] = new Rect(5, 8);System.out.println("========矩形周长和面积========");System.out.println(shape[1].getArea());System.out.println(shape[1].getPerimeter());shape[2] = new Square(5);System.out.println("========正方形周长和面积========");System.out.println(shape[2].getArea());System.out.println(shape[2].getPerimeter());}}每天进步一点点！