【Java基础】12.9习题(封装，继承)

水仙花数

import java.util.*; //万能头
public class Main
{
    public static void main(String[] args)
    {
        for(int i=100;i<1000;i++)
        {
            if(isYes(i))
            {
                System.out.println(i);
            }
        }
    }
    public static boolean isYes(int x)
    {
        int a=x/100,b=x/10%10,c=x%10;
        if(x==a*a*a+b*b*b+c*c*c) return true;
        else return false;
    }
}

练习题：面向对象 封装百分制分数
需求：封装百分制分数，和它对应的五档分制分数
分数类

public class Score {
    int score;
    char level;
    public Score(int score) {
        this.score = score;
        this.level = setLevel(score);
    }
    private char setLevel(int s) {
        char r = 0;
        switch(s/10)
        {
            case 10: case 9:
                r = 'A';
                break;
            case 8:case 7:
                r = 'B';
                break;
            case 6:
                r = 'C';
                break;
            case 5:case 4:case 3:case 2:
                r = 'D';
                break;
            case 1:case 0:
                r = 'E';
                break;
        }
        return r;
    }
    public String toString() {
        return score+", "+level;
    }
}

主函数

public class zhuhanshu
{
    public static void main(String[] args)
    {
        Score s = new Score(20);
        System.out.println(s.toString());
    }
}

练习题:面向对象 打印图形
需求：设计一个可以随机打印形状的代码
主函数

import java.util.*; //万能头
public class zhuhanshu
{
    public static void main(String[] args)
    {
        System.out.println("按回车继续");
        while(true) {
            int r = new Random().nextInt(4);
            switch(r)
            {
                case 0: f(new Shape()); break;
                case 1: f(new Line()); break;
                case 2: f(new Square()); break;
                case 3: f(new Circle()); break;
            }
        }
    }
    static void f(Shape s) {
        System.out.println("----------------");
        new Scanner(System.in).nextLine();
        s.draw();
        if(s instanceof Line)
        {
            Line line = (Line) s;
            line.length();
        }
        new Scanner(System.in).nextLine();
        s.clear();
    }
}

父类

public class Shape {
    public void draw()
    {
        System.out.println("图形形状");
    }
    public void clear()
    {
        System.out.println("\n\n\n");
    }
}

直线类

public class Line extends Shape {
    public void draw() {
        System.out.println("打印一条直线 ————");
    }
    public void length() {
        System.out.println("一米多。。。");
    }
}

圆形类

public class Circle extends Shape{
    public void draw()
    {
        System.out.println("打印一个圆形 o");
    }
}

方形类

public class Square extends Shape {
    public void draw()
    {
        System.out.println("打印一个方形 口");
    }
}