/*圆的类*/
public class R {
	 private double radius;

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

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

	    }
	    //求圆的周长
	    public double getPerimeter() {
	        return 2 * Math.PI * radius;
	    }
	    public void setRadius(double newRadius) {
	        this.radius=newRadius;
	    }

}

public class TR {
    public static void main(String[] args) {
        R circle1=new R();
        double area=circle1.getArea();
        System.out.println(area);
        R circle2=new R(20);
        System.out.println(circle2.getArea());
        System.out.println(circle1.getPerimeter());
        System.out.println(circle2.getPerimeter());
        double ridius=8;
        double areaCircle=Math.PI*ridius*ridius;
        System.out.println(areaCircle);
        circle2.setRadius(10);
        System.out.println(circle2.getArea());
    }
}

/*圆类的和并*/
public class TR {
	
	    private double radius;
	    public TR() {
	        this.radius=1;
	    }
	    public TR(double radius){
	        this.radius=radius;
	    }
	    public double getArea() {
	        return Math.PI*radius*radius;
	    }
	    public double getPerimeter() {
	        return 2*Math.PI*radius;
	    }
	    
	    public static void main(String[] args) {
	    	TR cir1=new TR();
	        System.out.println("The area of the circle of radius "+cir1.radius+" is "+cir1.getArea());
	        TR cir2=new TR(100);
	        System.out.println("The area of the circle of radius "+cir2.radius+" is "+cir2.getArea());
	    }
	
}

/*造电视*/
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--;
        }
    }
}

public class TextTV {

    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);
        
        
    }
}