Java基础 接口实现 设计一个形状类(接口)Shape,方法:求周长和求面积 |
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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; } @Override public double getArea() { // TODO Auto-generated method stub return PI * r * r; } @Override public double getPerimeter() { // TODO Auto-generated method stub return 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; } @Override public double getArea() { // TODO Auto-generated method stub return width * height; } @Override public double getPerimeter() { // TODO Auto-generated method stub return 2 * (width + height); } }正方形，继承矩形 public class Square extends Rect { public Square(double width) { super(width); } @Override public double getArea() { // TODO Auto-generated method stub return getWidth() * getWidth(); } @Override public double getPerimeter() { // TODO Auto-generated method stub return 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！ |
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