2019-12-18 · 多态性练习（几何图形）

废话不多说，题来！

GeometriceObject 类：

package com.it18;
/*
 * 该类代表几何形状
 */
public class GeometriceObject {

    
    protected String color;
    protected double weight;
    
    
    public GeometriceObject() {
        super();
    }
    public GeometriceObject(String color, double weight) {
        this.color = color;
        this.weight = weight;
    }

    
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    public double getWeight() {
        return weight;
    }
    public void setWeight(double weight) {
        this.weight = weight;
    }


    //不知道写声明，就先返回0.0
    public double findArea() {
        return 0.0;
    }
}

Circle 类：

package com.it18;
/*
 * 此类代表圆形
 */
public class Circle extends GeometriceObject{

    private double radius;
    
    
    public Circle() {
        super();
    }
    //父类中的属性，使用super();
    public Circle(double radius, String color, double weight) {
        super(color,weight);//回父类中找包含括号里面结构的构造器
        this.radius = radius;
    }
    
    public double getRadius() {
        return radius;
    }
    public void setRadius(double radius) {
        this.radius = radius;
    }
    
    public double findArea() {
        return Math.PI*radius*radius;
    }
}

MyRectangle 类：

package com.it18;
/*
 * 此类代表矩形
 */
public class MyRectangle extends GeometriceObject{

    private double width;
    private double height;
    
    
    public MyRectangle() {
        super();
    }
    //问题3：使用super(),回父类构造器中调用
    public MyRectangle(double width, double height, String color, double weight) {
        super(color, weight);
        this.width = width;
        this.height = height;
    }
    
    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;
    }
    
    public double findArea() {
        return width*height;
    }
}

GeometriceTest 测试类：

package com.it18;

public class GeometriceTest {
    public static void main(String[] args) {
        //创建本类的对象，调用本类的方法
        GeometriceTest test = new GeometriceTest();
        //创建圆的对象
        Circle c1 = new Circle(1, "white", 1.0);
        test.displayGeometriceObject(c1);
        Circle c2 = new Circle(2, "white", 1.0);
        test.displayGeometriceObject(c2);
        
        boolean equalsArea = test.equalsArea(c1, c2);
        System.out.println("c1和c2的面积是否相等：" + equalsArea);
        
        /*
         * 矩形的方法和圆一样，自行练习
         */
    }
    
    public void displayGeometriceObject(GeometriceObject o) {//多态：GeometriceObject o = new Circle(...);
        System.out.println("面积为：" + o.findArea());
    }
    public boolean equalsArea(GeometriceObject o1, GeometriceObject o2) {
        return o1.findArea() == o2.findArea();
    }
}

总结：

该练习遇到的问题：

1. 不熟悉子类调用父类的构造器。
2. 遇到不明返回值的方法，不知道怎么办。
3. 对多态性的理解不够，甚至题都有点看不懂。

加油吧...