chapter05--车辆，乡村用水，一元二次方程的根，电视频道

车辆

public class Vehicle {//声明变量     double speed;     int power;     //定义函数，体现机动车加速功能     void speedUp(int s){    //将参数s的值与成员变量speed的和赋值给成员变量speed     speed=speed+s;     }     //定义减速功能函数     void speedDown(int d){     //将成员变量speed与参数d的差值赋值给成员变量speed     speed=speed-d;     }     //获取机动车速度     double getSpeed(){    return speed;      }     //设置机动车功率    void setPower(int p){     //将参数p的值赋值给成员变量power    power=p;     }    //获取机动车功率    int getPower(){    return power;//返回成员变量power的值      }}

public class User {public static void main(String[] args){Vehicle car1,car2;//使用new运算符和默认的构造方法创建对象car1 car1=new Vehicle();//使用new运算符和默认的构造方法创建对象car2 car2=new Vehicle(); car1.setPower(128); car2.setPower(76); System.out.println("car1的功率是："+car1.getPower()); System.out.println("car2的功率是："+car2.getPower()); //car1调用speedUp()方法将自己的speed的值增加80 car1.speedUp(80);//car2调用speedUp()方法将自己的speed的值增加100 car2.speedUp(100); System.out.println("car1目前的速度："+car1.getSpeed()); System.out.println("car2目前的速度："+car2.getSpeed()); car1.speedDown(10); car2.speedDown(20); System.out.println("car1目前的速度："+car1.getSpeed()); System.out.println("car2目前的速度："+car2.getSpeed());}}

运行结果:

乡村用水：

package Drink;public class Land {   public static void main(String[] args){   Village.setWaterAmount(200);//用类名调用setWaterAmount(int m),并向参数传值200   int leftWater=Village.waterAmount;  //用Village类的类名访问waterAmount   System.out.println("水井中有"+leftWater+"升水");   Village zhaoZhuang,maJiaHeZi;   zhaoZhuang=new Village("赵庄");   maJiaHeZi=new Village("马家河子");   zhaoZhuang.setPeopleNumber(80);   maJiaHeZi.setPeopleNumber(120);   zhaoZhuang.drinkWater(50);//zhaoZhuang调用drinkWater(int n)，并向参数传值50   leftWater=Village.lookWaterAmount(); //maJiaHeZi调用lookWaterAmount()方法   String name=maJiaHeZi.name;   System.out.println(name+"发现水井中有"+leftWater+"升水");   maJiaHeZi.drinkWater(100);   leftWater=Village.lookWaterAmount();//zhaoZhuang调用lookWaterAmount()方法   name=zhaoZhuang.name;   System.out.println(name+"发现水井中有"+leftWater+"升水");   int peopleNumber=zhaoZhuang.getPeopleNumber();   System.out.println("赵庄的人口"+peopleNumber);   peopleNumber=maJiaHeZi.getPeopleNumber();   System.out.println("马家河子的人口:"+peopleNumber);   }}

package Drink;public class Village {   static int waterAmount;//模拟水井的水量   int peopleNumber;//村庄的人数   String name;   Village(String s){   name=s;   }   static void setWaterAmount(int m){   if(m>0)   waterAmount=m;   }   void drinkWater(int n){   if(waterAmount-n>=0){   waterAmount=waterAmount-n;   System.out.println(name+"喝了"+n+"升水");   }   else   waterAmount=0;   }   static int lookWaterAmount(){   return waterAmount;   }   void setPeopleNumber(int n){   peopleNumber=n;   }   int getPeopleNumber(){   return peopleNumber;   }}

运行结果：

一元二次方程的根：

package Square;public class SquareEquation {      double a,b,c;      double root1,root2;      boolean boo;      public SquareEquation(double a,double b,double c){      this.a=a;      this.b=b;      this.c=c;      if(a!=0)      boo=true;      else      boo=false;      }      public void getRoots(){      if(boo){      System.out.println("是一元二次方程");      double disk=b*b-4*a*c;      if(disk>=0){      root1=(-b+Math.sqrt(disk))/(2*a);      root2=(-b-Math.sqrt( disk))/(2*a);      System.out.printf("方程的根：%f,%f\n",root1,root2);      }      else{      System.out.printf("方程没有实根\n");      }      }      else{      System.out.println("不是一元二次方程");      }      }      public void setCoefficient(double a,double b,double c){      this.a=a;      this.b=b;      this.c=c;      if(a!=0)      boo=true;      else      boo=false;      }}

package Square;import Square.*;public class SunRise {     public static void main(String[] args){     SquareEquation equation=new SquareEquation(4,5,1);     equation.getRoots();     equation.setCoefficient(-3,4,5);     equation.getRoots();     }}

运行结果：

电视频道：

package Television;public class Family {TV homeTV;void buyTV(TV tv){//将参数tv赋值给homeTVhomeTV=tv;}void remoteControl(int m){homeTV.setChannel(m);}void seeTV(){homeTV.showProgram();//homeTV调用showProgram()方法}}package Television;public class MainClass {public static void main(String[] args){TV haierTV=new TV();haierTV.setChannel(5);//haierTV调用setChannel(int m),并向参数m传递5System.out.println("haierTV的频道是"+haierTV.getChannel());Family zhangsanFamily=new Family();zhangsanFamily.buyTV(haierTV);//zhangsanFamily调用void buyTV(TV tv)方法,并将haierTV传递给参数TVSystem.out.println("zhangsanFamily开始看电视节目");zhangsanFamily.seeTV();int m=2;System.out.println("zhangsanFamily将电视更换到"+m+"频道");zhangsanFamily.remoteControl(m);System.out.println("haierTV的频道是"+haierTV.getChannel());System.out.println("zhangsanFamily再看电视节目");zhangsanFamily.seeTV();}}package Television;public class TV {     int channel;//电视频道     //设置电视频道     void setChannel(int m){     if(m>=1){     channel=m;     }     }     //获取电视频道     int getChannel(){     return channel;     }     //展示节目     void showProgram(){     switch(channel){     case 1:System.out.println("综合频道");            break;     case 2:System.out.println("经济频道");        break;     case 3:System.out.println("文艺频道");        break;     case 4:System.out.println("国际频道");        break;     case 5:System.out.println("体育频道");        break;     default:System.out.println("不能收看"+channel+"频道");     }     }}

运行结果：