练习9（第九章习题）

package cn.ch.w;

public class TestSimpleCircle {
    private double radius;

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

package cn.ch.w;

public class DemoCircle {
     public static void main(String[] args) {
             TestSimpleCircle circle1=new TestSimpleCircle();
            double area=circle1.getArea();
            System.out.println(area);
            TestSimpleCircle circle2=new TestSimpleCircle();
            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());
        }


}

9-2

package cn.ch.w;

public class SimpleCircle {
    private double radius;
    public SimpleCircle() 
    {
        this.radius=1;
    }
    public SimpleCircle(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)
    {
        SimpleCircle cir1=new SimpleCircle();
        System.out.println("半径是"+cir1.radius+"面积是"+cir1.getArea());
        SimpleCircle cir2=new SimpleCircle(10);
        System.out.println("半径是"+cir2.radius+"面积是"+cir2.getArea());
    }


}

9-3

package cn.ch.w;

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("电视已开启！！");
    }
    public void turnOff() 
    {
        on=false;
        System.out.println("电视已关闭！！");
    }
    public int getChannel() 
    {
        return channel;
    }
    public void setChannel(int channel) 
    {
        if(on) 
        {
            System.out.println("电视机已开，可以调试了。");
            if(channel>=1&&channel<=120) 
            {
                this.channel = channel;
                System.out.println("频道已在"+channel+" 台");
            }else 
            {
                System.out.println("频道不存在！！");
            }
        }else 
        {
            System.out.println("白痴主人电视开启才可以调试");
        }
    }
    public int getVolumeLevel() 
    {
        return volumeLevel;
    }
    public void setVolumeLevel(int volumeLevel) {
        if(on) {
            System.out.println("电视已开，声音已可调试");
            if(volumeLevel>=1&&volumeLevel<=7) {
                this.volumeLevel = volumeLevel;
                System.out.println("声音设置成了 "+volumeLevel+" 大小");
            }
        }else 
        {
            System.out.println("白痴主人电视开启才可以调试");
        }
        
    }
    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--;
        }
    }


}

package cn.ch.w;

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("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.channelUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.channelUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.channelUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.volumeUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.volumeUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      tv2.volumeUp();
      System.out.println("电视节目是"+tv2.channel+"声音是"+tv2.volumeLevel);
      
      
  }


}