实验五-继承与接口
实验五 继承与接口 1.实验目的 1、掌握类的继承细节内容，包括子类的继承、子类对象创建、成员变量的继承与隐藏、方法的继承与重写 2、掌握重写的目的以及怎样使用 super 关键字 3、掌握上转型对象与接口回调技术 4、掌握类怎样实现接口，及面向接口的编程思想 2.实验内容 1、根据附录里的源代码，按照注释要求，完成代码填空，使程序能够运行得出结果。
1）实验 1 中国人与美国人 package boy;public class People { protected double weight ,height;public void speakHello(){ System.out.println("yayayaya");} public void averageHeight(){ height=173;System.out.println("average height:"+height);} public void averageWeight(){ weight=70;System.out.println("average weight:"+weight);} } package boy;public class ChinaPeople extends People{ public void speakHello(){ System.out.println("你好");} public void averageHeight(){ height=168.78;System.out.println("中国人的平均身高:"+height+"厘米");} public void averageWeight(){ weight=65;System.out.println("中国人的平均体重:"+weight+"公斤");}
//【代码 1】//重写 public void averageWeight()方法,输出:"中国人的平均体重:65公斤" public void chinaGongfu(){ System.out.println("坐如钟,站如松,睡如弓");} } package boy;public class AmericanPeople extends People{ public void speakHello(){ System.out.println("How do you do");} public void averageHeight(){ System.out.println("American"s average height:176cm");} //【代码 2】//重写 public void speakHello()方法,输出:"How do you do" //【代码 3】//重写 public void averageHeight()方法,输出:"American"s average height:176cm" public void averageWeight(){ weight=75;System.out.println("American"s average weight:"+weight+"kg");} public void americanBoxing(){ System.out.println("直拳、钩拳、组合拳");} } package boy;public class BeijingPeople extends ChinaPeople{ public void averageHeight(){ System.out.println("北京人的平均身高:172.5 厘米");} public void averageWeight(){ System.out.println("北京人的平均体重:70 公斤");} // 【代码 4】//重写 public void averageHeight()方法,输出:"北京人的平均身高:172.5厘米" //【代码 5】//重写 public void averageWeight()方法,输出:"北京人的平均体重:70公斤" public void beijingOpera(){ System.out.println("花脸、青衣、花旦和老生");} }
package boy;public class Example { public static void main(String[] args){ ChinaPeople chinaPeople = new ChinaPeople();AmericanPeople americanPeople = new AmericanPeople();BeijingPeople beijingPeople = new BeijingPeople();chinaPeople.speakHello();americanPeople.speakHello();beijingPeople.speakHello();chinaPeople.averageHeight();americanPeople.averageHeight();beijingPeople.averageHeight();chinaPeople.averageWeight();americanPeople.averageWeight();beijingPeople.averageWeight();chinaPeople.chinaGongfu();americanPeople.americanBoxing();beijingPeople.beijingOpera();beijingPeople.chinaGongfu();} } 你好 How do you do 你好 中国人的平均身高:168.78 厘米 American"s average height:176cm 北京人的平均身高:172.5 厘米 中国人的平均体重:65.0 公斤 American"s average weight:75.0kg 北京人的平均体重:70 公斤 坐如钟,站如松,睡如弓 直拳、钩拳、组合拳 花脸、青衣、花旦和老生 坐如钟,站如松,睡如弓 2）实验 2 银行与利息 package boy;public class Bank { int savedMoney;int year;double interest;double interestRate=0.29;
public double computerInterest(){ interest=year*interestRate*savedMoney;return interest;} public void setInterestRate(double rate){ interestRate = rate;} } package boy;public class ConstructionBank extends Bank{ double year;public double computerInterest(){ super.year=(int)year;double r=year-(int)year;int day=(int)(r*1000);double yearInterest=super.computerInterest();//【代码 1】//super 调用隐藏的 computerInterest()方法 double dayInterest=day*0.0001*savedMoney;interest=yearInterest+dayInterest;System.out.printf("%d 元存在建设银行%d 年零%d 天的利息：%f 元n",savedMoney,super.year,day,interest);return interest;} } package boy;public class BankOfDalian extends Bank{ double year;public double computerInterest(){ super.year=(int)year;double r=year-(int)year;int day=(int)(r*1000);double yearInterest=super.computerInterest();//【代码 2】//super 调用隐藏的 computerInterest()方法 double dayInterest=day*0.00012*savedMoney;interest=yearInterest+dayInterest;System.out.printf("%d 元存在大连银行%d 年零%d 天的利息：%f 元n",savedMoney,super.year,day,interest);return interest;} } package boy;
public class SaveMoney { public static void main(String[] args){ int amount=8000;ConstructionBank bank1=new ConstructionBank();bank1.savedMoney=amount;bank1.year=8.236;bank1.setInterestRate(0.035);double interest1=bank1.computerInterest();BankOfDalian bank2=new BankOfDalian();bank2.savedMoney=amount;bank2.year=8.236;bank2.setInterestRate(0.035);double interest2=bank2.computerInterest();System.out.printf("两个银行利息相差%f 元n",interest2-interest1);} } 8000 元存在建设银行 8 年零 236 天的利息：2428.800000 元 8000 元存在大连银行 8 年零 236 天的利息：2466.560000 元 两个银行利息相差 37.760000 元 3）实验 3 面积之和 Geometry.java public abstract class Geometry { public abstract double getArea();} package boy;public class TotalArea { Geometry[] tuxing;double totalArea=0;public void setTuxing(Geometry[] t){ tuxing=t;} public double computerTatalArea(){ for(int i=0;i } } package boy;public class Rect extends Geometry{ double a,b;Rect(double a,double b){ this.a=a;this.b=b;} public double getArea(){ return a*b;} }//【代码 1】//重写 getArea()方法 package boy;public class Circle extends Geometry{ double r;Circle(double r){ this.r=r;} public double getArea(){ return 3.14*r*r;}//【代码 2】//重写 getArea()方法 } package boy;public class MainClass { public static void main(String[] args){ Geometry[] tuxing=new Geometry[29];//有 29 个 Geometry 对象 for(int i=0;i 各种图形的面积之和： 58778.360000 4）实验 4 歌手大赛 package boy;public interface ComputerAverage { public double average(double x[]);} package boy;public class SongGame implements ComputerAverage{ public double average(double x[]){ int count=x.length;double aver=0,temp=0;for(int i=0;i average(double x[])方法，返回数组 x[]的元素的算术平方 double sum=0;for(int i=0;i } } package boy;public class CloudyLittleState implements WeatherState{ public void showState(){ System.out.print("少云，有时晴。");} } package boy;public class HeavyRainState implements WeatherState{ public void showState(){ //【代码 2】//重写 public void showState()方法 System.out.print("暴雨，有闪电。");} } package boy;public class LightRainState implements WeatherState{ public void showState(){ //【代码 2】//重写 public void showState()方法 System.out.print("小雨，转多云。");} } package boy;public interface WeatherState { public void showState();//重写 public void showState()方法 } package boy;public class WeatherForecast { public static void main(String[] args){ Weather weatherBeijing=new Weather();System.out.print("n 今天白天：");weatherBeijing.setState(new CloudyDayState());weatherBeijing.show();System.out.print("n 今天夜间：");weatherBeijing.setState(new LightRainState());weatherBeijing.show();System.out.print("n 转：");weatherBeijing.setState(new HeavyRainState()); weatherBeijing.show();System.out.print("n 明天白天：");weatherBeijing.setState(new LightRainState());weatherBeijing.show();System.out.print("n 明天夜间：");weatherBeijing.setState(new CloudyLittleState());weatherBeijing.show();} } 今天白天：少云，有时晴。 今天夜间：小雨，转多云。 转：暴雨，有闪电。 明天白天：小雨，转多云。 明天夜间：少云，有时晴。 2、设计编写程序完成以下任务。 1）根据要求修改实验 2，参照建设银行再编写一个商业银行（广发行），让程序输出 8000 元在广发行 8 年零 212 天的利息。 package boy;public class Bank { int savedMoney;int year;double interest;double interestRate=0.29;public double computerInterest(){ interest=year*interestRate*savedMoney;return interest;} public void setInterestRate(double rate){ interestRate = rate;} } package boy;public class ConstructionBank extends Bank{ double year;public double computerInterest(){ super.year=(int)year;double r=year-(int)year;int day=(int)(r*1000);double yearInterest=super.computerInterest();//【代码 1】//super 调用隐 藏的 computerInterest()方法 double dayInterest=day*0.0001*savedMoney;interest=yearInterest+dayInterest;System.out.printf("%d 元存在建设银行%d 年零%d 天的利息：%f 元n",savedMoney,super.year,day,interest);return interest;} } package boy;public class SaveMoney { public static void main(String[] args){ int amount=8000;ConstructionBank bank1=new ConstructionBank();bank1.savedMoney=amount;bank1.year=8.212;bank1.setInterestRate(0.035);double interest1=bank1.computerInterest();} } 2）根据要求修改实验3，再增加一种几何图形（梯形），并让主类中的tuxing的某些元素是梯形的上转型对象。 package four1;public abstract class Geometry { public abstract double getArea();} package four1;public class TotalArea { Geometry[] tuxing;double totalArea=0;public void setTuxing(Geometry[] t){ tuxing=t;} public double computerTatalArea(){ for(int i=0;i } //【代码 3】//用循环语句让 tuxing 的元素调用 getArea 方法，并将返回的值累加到 totalArea return totalArea;} } package four1;public class Trapezoid extends Geometry{ double x,y,z;Trapezoid(double x,double y,double z){ this.x=x;this.y=y;this.z=z;} public double getArea(){ return z*(x+y)/2;} } package four1;public class MainClass { public static void main(String[] args){ Trapezoid tuxing=new Trapezoid(4.6,4.6,7.9);//有 29 个 Geometry 对象 double s=tuxing.getArea();System.out.printf("梯形的面积为:n%f",s);} } 3）仿照实验5编写一个程序实现模拟水杯中的水在不同温度下可能出现的状态。 package four1;public class BoiledState implements WaterState{ public void showState(){ System.out.println("开水。");} } package four1; public class IceState implements WaterState{ public void showState(){ System.out.print("结冰。");} } package four1;public class LittleWarmState implements WaterState{ public void showState(){ System.out.println("微凉。");} } package four1;public class WarmState implements WaterState{ public void showState(){ System.out.println("温水。");} //【代码 2】//重写 public void showState()方法 } package four1;public class Water { WaterState state;public void show(){ state.showState();} public void setState(WaterState s){ state=s;} } package four1;public class WaterForecast { public static void main(String[] args){ Water waterState=new Water();System.out.print("n 温度在 90-100 时水杯水的状态：");waterState.setState(new BoiledState());waterState.show();System.out.print("n 温度在 50--80 时水杯水的状态：");waterState.setState(new WarmState());waterState.show(); System.out.print("n 温度在 30-50 时水杯水的状态：");waterState.setState(new LittleWarmState());waterState.show();System.out.print("n 温度在 0 度下时水杯水的状态：");waterState.setState(new IceState());waterState.show();} } package four1;public interface WaterState { public void showState();} 实验结果 4）编写一个接口并创建两个实现该接口的类 A、B。A、B 类实现了接口的 f方法，A 类的 f 方法内容为计算 1！+3！+5！……+9！并返回结果，B 类的 f 方法内容为计算 2！+4！+6！……+10！也返回结果；再编一个执行类，执行类运行时要求通过接口回调方式用同一个对象实例分别调用 A 类的 f 方法和 B 类的 f方法。 package four1;public class A implements object { public int f(int a, int b){ int sum=0,temp=1;for(int i=a;i<=b;i=i+2){ for(int j=1;j<=i;j++){ temp*=j;} sum+=temp;temp=1;} return sum;} } package four1;public class B implements object { public int f(int a, int b){ int sum=0,temp=1;for(int i=a;i<=b;i=i+2){ for(int j=1;j<=i;j++){ temp*=j;} sum+=temp;temp=1;} return sum;} } package four1;public interface object { int f(int a,int b);} package four1;public class Test { public static void main(String[] args){ A a=new A();B b=new B();int sum1=a.f(1, 9);int sum2=b.f(2, 10);System.out.println("1！+3！+5！……+9！的结果为："+sum1);System.out.println("2！+4！+6！……+10！的结果为："+sum2);} } 实验结果 5）(1)定义一个汽车类 Vehicle，要求如下：（知识点：类的继承 方法的覆盖）（a）属性包括：汽车品牌 brand（String 类型）、颜色 color（String 类型）和速度 speed（double 类型）。 （b）至少提供一个有参的构造方法（要求品牌和颜色可以初始化为任意值，但速度的初始值必须为 0）。 （c）为属性提供访问器方法。注意：汽车品牌一旦初始化之后不能修改。 （d）定义一个一般方法 run()，用打印语句描述汽车奔跑的功能。 定义测试类 VehicleTest，在其 main 方法中创建一个品牌为“benz”、颜色为“black”的汽车。 (2)定义一个 Vehicle 类的子类轿车类 Car，要求如下： （a）轿车有自己的属性载人数 loader（int 类型）。 （b）提供该类初始化属性的构造方法。 （c）重新定义 run()，用打印语句描述轿车奔跑的功能。 （d）定义测试类 Test，在其 main 方法中创建一个品牌为“Honda”、颜色为“red”，载人数为 2 人的轿车。 面向对象基础出过类似的，这个把继承引入了 package four1;public class Car extends Vehicle { int loader;public Car(String brand, String color, double speed,int l){ super(brand, color, speed);this.loader=l;} public void run(){ System.out.println("颜色为"+super.getColor()+"的"+super.getBrand()+"汽车的时速为："+super.getSpeed());} } package four1; public class Test { public static void main(String[] args){ Car c=new Car("Honda","red",300.0,20);c.run();} } package four1;public class Vehicle { private String brand="BMW";//汽车品牌 private String color="red";//汽车颜色 private double speed=0;//汽车时速 public String getColor(){ return color;} public void setColor(String color){ this.color = color;} public double getSpeed(){ return speed;} public void setSpeed(double speed){ this.speed = speed;} public String getBrand(){ return brand;} public Vehicle(String brand, String color, double speed){ this.brand=brand;this.color=color;this.speed=speed;} public void run(){ System.out.println(brand+"汽车的时速为："+speed);} } package four1; public class VehicleTest { public static void main(String[] args){ Vehicle v=new Vehicle("benz","black",200.0);v.run();} } 实验结果 6）Cola 公司的雇员分为以下若干类：(知识点：多态)(1)ColaEmployee ：这是所有员工总的父类，属性：员工的姓名,员工的生日月份。 方法：getSalary(int month)根据参数月份来确定工资，如果该月员工过生日，则公司会额外奖励 100 元。 (2)SalariedEmployee ： ColaEmployee 的子类，拿固定工资的员工。 属性：月薪(3)HourlyEmployee ：ColaEmployee 的子类，按小时拿工资的员工，每月工作超出 160 小时的部分按照 1.5 倍工资发放。 属性：每小时的工资、每月工作的小时数(4)SalesEmployee ：ColaEmployee 的子类，销售人员，工资由月销售额和提成率决定。 属性：月销售额、提成率(5)定义一个类 Company，在该类中写一个方法，调用该方法可以打印出某月某个员工的工资数额，写一个测试类 TestCompany,在 main 方法，把若干各种类型的员工放在一个 ColaEmployee 数组里，并单元出数组中每个员工当月的工资。 知识点：继承与多态 package four1;public class ColaEmployee { String name;//员工姓名 int month;//员工生日月份 public String getName(){ return name;} public void setName(String name){ this.name = name;} public int getMonth(){ return month;} public void setMonth(int month){ this.month = month;} int getSalary(int month){ if(month == this.month){ return 100;} else { return 0;} } } package four1;public class Company extends ColaEmployee{ void print(String name, double salary,int month){ String Name=name;double Salary=salary;int Month=month;System.out.println("员工"+Name+"在"+Month+"月"+"的薪资为："+Salary);} } package four1;public class HourlyEmployee extends ColaEmployee { double hours;//每月工作的时间 double hsalary;//每小时的工资 Company c=new Company();public HourlyEmployee(String name,int month, double hours, double hsalary){ this.hours=hours;this.hsalary=hsalary;this.month=month;this.name=name;} public double getHours(){ return hours;} public void setHours(double hours){ this.hours = hours;} public double getHsalary(){ return hsalary;} public void setHsalary(double hsalary){ this.hsalary = hsalary;} public int getSalary(int month){ if(this.hours<=160){ this.hsalary=this.hsalary*this.hours+super.getSalary(month);c.print(name,hsalary,month);return 0;} else { this.hsalary=(this.hours-160)*this.hsalary*1.5+160*this.hsalary+super.getSalary(month);c.print(name,hsalary,month);return 0;} } } package four1;public class SalariedEmployee extends ColaEmployee { double salary;//员工固定薪资（按月）Company c=new Company();public SalariedEmployee(String name, int month, double salary){ this.name=name;this.month=month;this.salary=salary;} public int getSalary(int month){ this.salary=salary + super.getSalary(month);c.print(name,salary,month);return 0;} } package four1;public class SalesEmployee extends ColaEmployee{ double money;//月销售额 double ticheng;//提成率 Company c=new Company();public SalesEmployee(String name, int month, double money, double ticheng){ this.money=money;this.month=month;this.name=name;this.ticheng=ticheng;} public double getMoney(){ return money;} public void setMoney(double money){ this.money = money;} public double getTicheng(){ return ticheng;} public void setTicheng(double ticheng){ this.ticheng = ticheng;} public int getSalary(int month){ this.money= money + super.getSalary(month)+(money*ticheng);c.print(name,money,month);return 0;} } package four1;public class SalesEmployee extends ColaEmployee{ double money;//月销售额 double ticheng;//提成率 Company c=new Company();public SalesEmployee(String name, int month, double money, double ticheng){ this.money=money;this.month=month;this.name=name;this.ticheng=ticheng;} public double getMoney(){ return money;} public void setMoney(double money){ this.money = money;} public double getTicheng(){ return ticheng;} public void setTicheng(double ticheng){ this.ticheng = ticheng;} public int getSalary(int month){ this.money= money + super.getSalary(month)+(money*ticheng);c.print(name,money,month);return 0;} } package four1;public class TestCompany { public static void main(String[] args){ ColaEmployee[] ce =new ColaEmployee[3];ce[0]=new SalariedEmployee("aa",9,3000.0);ce[1]=new HourlyEmployee("bb",3,2000.0,180);ce[2]=new SalesEmployee("cc",6,6000,0.3);ce[0].getSalary(2);ce[1].getSalary(2); ce[2].getSalary(2);} } 实验结果 7）利用接口实现动态的创建对象：（知识点：接口）（1）创建 4 个类 1 苹果 2 香蕉 3 葡萄 4 园丁（2）在三种水果的构造方法中打印一句话.以苹果类为例 class apple { public apple(){ System.out.println(“创建了一个苹果类的对象”);} }（3）类图如下： ApplePearOranges+create(): FruitGardener<<接口>>Fruit（4）要求从控制台输入一个字符串，根据字符串的值来判断创建三种水果 中哪个类的对象。 运行结果如图： package four1;public class apple implements Fruit { public void apple(){ System.out.println("创建了一个苹果类的对象");} public void banana(){ } public void pear(){ } } package four1;public class banana implements Fruit { public void banana(){ System.out.println("创建了一个香蕉类的对象");} public void apple(){ } public void pear(){ } } package four1;public interface Fruit { void apple();void banana();void pear();} package four1;public class pear implements Fruit { public void pear(){ System.out.println("创建了一个梨子类的对象");} public void apple(){ } public void banana(){ } } package four1;import java.util.Scanner;public class Test { public static void main(String[] args){ Scanner input=new Scanner(System.in);System.out.println("请输入您要创建的类：");String attr=input.nextLine();if(attr.equals("banana")){ Fruit fruit=new banana();fruit.banana();} else if(attr.equals("apple")){ Fruit fruit = new apple();fruit.apple();} else if(attr.equals("pear")){ Fruit fruit =new pear(); fruit.pear();} else System.out.println("输入有误！");} } 实验结果 3.实验步骤 略 4.评分标准 1.A——内容功能完善，编程风格好，人机接口界面好； 2.B——内容功能完善，编程风格良好，人机接口界面良好； 3.C——完成必做内容； 4.D——能完成必做内容； 5.E——未按时完成必做内容，或者抄袭（雷同者全部为 E）.参照书上实验按模版要求，将【代码】替换为 Java 程序代码，编写好完整的程序文档，最后运行得到的相关文件，把实验所得文件一起打包上交。（压缩包的文件名为：学号后三位和名字开头字母，如 109zhh．RAR|ZIP） 附录： 验 实验 1 中国人与美国人 模板代码 People.java public class People { protected double weight ,height;public void speakHello(){ System.out.println("yayayaya");} public void averageHeight(){ height=173;System.out.println("average height:"+height);} public void averageWeight(){ weight=70;System.out.println("average weight:"+weight);} } ChinaPeople.java public class ChinaPeople extends People{ public void speakHello(){ System.out.println("你好");} public void averageHeight(){ height=168.78;System.out.println("中国人的平均身高:"+height+"厘米");} //【代码 1】//重写 public void averageWeight()方法,输出:"中国人的平均体重:65 公斤" public void chinaGongfu(){ System.out.println("坐如钟,站如松,睡如弓");} } AmericanPeople.java public class AmericanPeople extends People{ //【代码 2】//重写 public void speakHello()方法,输出:"How do you do" // 【代码 3】//重写 public void averageHeight()方法,输出:"American"s average height:176cm" public void averageWeight(){ weight=75;System.out.println("American"s average weight:"+weight+"kg");} public void americanBoxing(){ System.out.println("直拳、钩拳、组合拳");} } BeijingPeople.java public class BeijingPeople extends ChinaPeople{ //【代码 4】//重写 public void averageHeight()方法,输出:"北京人的平均身高:172.5 厘米" //【代码 5】//重写 public void averageWeight()方法,输出:"北京人的平均体重:70 公斤" public void beijingOpera(){ System.out.println("花脸、青衣、花旦和老生");} } Example.java public class Example { public static void main(String[] args){ ChinaPeople chinaPeople = new ChinaPeople();AmericanPeople americanPeople = new AmericanPeople();BeijingPeople beijingPeople = new BeijingPeople();chinaPeople.speakHello();americanPeople.speakHello();beijingPeople.speakHello();chinaPeople.averageHeight();americanPeople.averageHeight();beijingPeople.averageHeight();chinaPeople.averageWeight();americanPeople.averageWeight();beijingPeople.averageWeight();chinaPeople.chinaGongfu();americanPeople.americanBoxing();beijingPeople.beijingOpera();beijingPeople.chinaGongfu();} } 验 实验 2 银行与利息 模板代码 Bank.java public class Bank { int savedMoney;int year;double interest;double interestRate=0.29;public double computerInterest(){ interest=year*interestRate*savedMoney;return interest;} public void setInterestRate(double rate){ interestRate = rate;} } ConstructionBank.java public class ConstructionBank extends Bank{ double year;public double computerInterest(){ super.year=(int)year;double r=year-(int)year;int day=(int)(r*1000);double yearInterest=//【代码 1】//super 调用隐藏的 computerInterest()方法 double dayInterest=day*0.0001*savedMoney;interest=yearInterest+dayInterest;System.out.printf("%d 元 存 在 建 设 银 行 %d 年 零 %d 天 的 利 息 ： %f 元n",savedMoney,super.year,day,interest);return interest;} } BankOfDalian.java public class BankOfDalian extends Bank{ double year;public double computerInterest(){ super.year=(int)year;double r=year-(int)year;int day=(int)(r*1000);double yearInterest=//【代码 2】//super 调用隐藏的 computerInterest()方法 double dayInterest=day*0.00012*savedMoney;interest=yearInterest+dayInterest;System.out.printf("%d 元 存 在 大 连 银 行 %d 年 零 %d 天 的 利 息 ： %f 元n",savedMoney,super.year,day,interest);return interest; } } SaveMoney.java public class SaveMoney { public static void main(String[] args){ int amount=8000;ConstructionBank bank1=new ConstructionBank();bank1.savedMoney=amount;bank1.year=8.236;bank1.setInterestRate(0.035);double interest1=bank1.computerInterest();BankOfDalian bank2=new BankOfDalian();bank2.savedMoney=amount;bank2.year=8.236;bank2.setInterestRate(0.035);double interest2=bank2.computerInterest();System.out.printf("两个银行利息相差%f 元n",interest2-interest1);} } 验 实验 3 面积之和 模板代码 Geometry.java public abstract class Geometry { public abstract double getArea();} TotalArea.java public class TotalArea { Geometry[] tuxing;double totalArea=0;public void setTuxing(Geometry[] t){ tuxing=t;} public double computerTatalArea(){ for(int i=0;i 到 totalArea return totalArea;} } Rect.java public class Rect extends Geometry{ double a,b;Rect(double a,double b){ this.a=a;this.b=b;} public double getArea(){ return a*b;} }//【代码 1】//重写 getArea()方法 Trapezoid.java public class Trapezoid extends Geometry{ double x,y,z;Rect(double x,double y,double z){ this.x=x;this.y=y;This.z=z;} public double getArea(){ return z*(x+y)/2;} } Circle.java public class Circle extends Geometry{ double r;Circle(double r){ this.r=r;} public double getArea(){ return 3.14*r*r;}//【代码 2】//重写 getArea()方法 } MainClass.java public class MainClass { public static void main(String[] args){ Trapezoid tuxing=new Trapezoid(4.6,4.6,7.9);//有 29 个 Geometry 对象 double s=tuxing.getArea();System.out.print(“梯形的面积为:n%f”,s);Geometry[] tuxing=new Geometry[29];//有 29 个 Geometry 对象 for(int i=0;i } if(count>2){ aver=aver/(count-2);}else{ aver=0;} return aver;} } School.java public class School implements ComputerAverage{ //【代码 1】//重写 public double average(double x[])方法，返回数组 x[]的元素的算术平方 } Estimator.java public class Estimator { public static void main(String[] args){ double a[]={};double b[]={};ComputerAverage computer;computer=new SongGame();double result=//【代码 2】//computer 调用 average(x[])方法，将数组 a 传递给参数 x System.out.printf("%n");System.out.printf("歌手最后得分：%5.3fn",result);computer=new School();result=//【代码 3】//computer 调用 average(x[])方法，将数组 b 传递给参数 x System.out.printf("学生平均体重：%-5.2f kg",result);} } 验 实验 5 天气预报 模板代码 WeatherState.java public interface WeatherState { public void showState();} Weather.java public class Weather { WeatherState state;public void show(){ state.showState();} public void setState(WeatherState s){ state=s;} } CloudyLittleState.java public class CloudyLittleState implements WeatherState{ public void showState(){ System.out.print("少云，有时晴。");} } CloudyDayState.java public class CloudyDayState implements WeatherState{ //【代码 1】//重写 public void showState()方法 } HeavyRainState.java public class HeavyRainState implements WeatherState{ //【代码 2】//重写 public void showState()方法 } LightRainState.java public class LightRainState implements WeatherState{ //【代码 3】//重写 public void showState()方法 } WeatherForecast.java public class WeatherForecast { public static void main(String[] args){ Weather weatherBeijing=new Weather();System.out.print("n 今天白天：");weatherBeijing.setState(new CloudyDayState());weatherBeijing.show(); System.out.print("n 今天夜间：");weatherBeijing.setState(new LightRainState());weatherBeijing.show();System.out.print("n 转：");weatherBeijing.setState(new HeavyRainState());weatherBeijing.show();System.out.print("n 明天白天：");weatherBeijing.setState(new LightRainState());weatherBeijing.show();System.out.print("n 明天夜间：");weatherBeijing.setState(new CloudyLittleState());weatherBeijing.show();} }
