java第九次作业：第九章例题3个

作业1：

例题9.1 制作圆类，根据圆的半径求出周长及面积

package com.swift;
//抽象的方法构成类，把属性和方法进行封装
public class Circle {
    // 两个方面一个是字段也称属性，另一个是方法，也称实现的功能
    private double radius;

    // 构造方法,有参构造
    public Circle(double radius) {
        this.radius = radius;
    }
    //方法的重载，参数不同
    // 构造方法，无参构造
    public Circle() {
        this.radius = 1;
    }

    // 求圆面积的方法
    public double getArea() {
        return radius * radius * Math.PI;

    }

    // 求圆周长的方法
    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }
    public void setRadius(double newRadius) {
        this.radius=newRadius;
    }
}

圆类的展示类

package com.swift;

public class DemoCircle {
    public static void main(String[] args) {
        Circle circle1=new Circle();
        double area=circle1.getArea();
        System.out.println(area);
        Circle circle2=new Circle(10);
        System.out.println(circle2.getArea());
        System.out.println(circle1.getPerimeter());
        System.out.println(circle2.getPerimeter());
        double ridius=10;
        double areaCircle=Math.PI*ridius*ridius;
        System.out.println(areaCircle);
        circle2.setRadius(5);
        System.out.println(circle2.getArea());
    }
}

作业2：

把上边的两个圆的类合并成一个类，并实现同样功能

package com.swift;

public class SimpleCircle {

    private double radius;
    public SimpleCircle() {
        this.radius=1;
    }
    public SimpleCircle(double radius){
        this.radius=radius;
    }
    public double getArea() {
        // TODO Auto-generated method stub
        return Math.PI*radius*radius;
    }
    public double getPerimeter() {
        return 2*Math.PI*radius;
    }

    public static void main(String[] args) {
        SimpleCircle cir1=new SimpleCircle();
        System.out.println("The area of the circle of radius "+cir1.radius+" is "+cir1.getArea());
        SimpleCircle cir2=new SimpleCircle(10);
        System.out.println("The area of the circle of radius "+cir2.radius+" is "+cir2.getArea());
    }
}

作业3：

例题9.3 造一台电视机，并且实现调频道和调声音大小功能

package com.swift;

public class TV {
    public int channel=1;
    public int volumeLevel=1;
    public boolean on=false;

    public TV() {

    }
    public void turnOn() {
        on =true;
        System.out.println("电视机已经打开了。");
    }
    public void turnOff() {
        on=false;
        System.out.println("电视机已经关闭了。");
    }
    public int getChannel() {
        return channel;
    }
    public void setChannel(int channel) {
        if(on) {
            System.out.println("电视机已开，可以开始调台了。");
            if(channel>=1&&channel<=120) {
                this.channel = channel;
                System.out.println("频道已经调到 "+channel+" 台");
            }else {
                System.out.println("你要调的频道不存在。");
            }
        }else {
            System.out.println("电视机关着的时候是不能调台的");
        }
    }
    public int getVolumeLevel() {
        return volumeLevel;
    }
    public void setVolumeLevel(int volumeLevel) {
        if(on) {
            System.out.println("电视机已开，声音大小可调了");
            if(volumeLevel>=1&&volumeLevel<=7) {
                this.volumeLevel = volumeLevel;
                System.out.println("声音的大小设置成了 "+volumeLevel+" 大小");
            }
        }else {
            System.out.println("电视机关着的时候是不能调声音的");
        }

    }
    public void channelUp() {
        if(on&&channel<120) {
            channel++;
        }
    }
    public void channelDown() {
        if(on&&channel>1) {
            channel--;
        }
    }
    public void volumeUp() {
        if(on&&volumeLevel<7) {
            volumeLevel++;
        }
    }
    public void volumeDown() {
        if(on&&volumeLevel>1) {
            volumeLevel--;
        }
    }

}

测试电视机的类

package com.swift;

public class TestTV {

    public static void main(String[] args) {
//        TV tv1=new TV();
//        tv1.turnOff();
//        tv1.setChannel(30);
//        tv1.setVolumeLevel(3);

        TV tv2=new TV();
        tv2.turnOn();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.channelUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.channelUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.channelUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.volumeUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.volumeUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);
        tv2.volumeUp();
        System.out.println("TV2's channel is "+tv2.channel+" and volume is "+tv2.volumeLevel);

    }

}