李晓菁201771010114《面向对象程序设计（Java）》第六周学习总结

Posted 2021-01-11 li-xiaojing

理论部分：

第五章：继承

1.继承用已有类来构建新类的一种机制。

2..继承的特点：具有层次结构，子类继承了父类的域和方法。

3.继承的优点：代码可重用性，父类的域和方法可用于子类，可以轻松定义子类，设计应用程序变得更加简单。

4.继承层次：

实验六 继承定义与使用

实验时间 2018-9-28

1、实验目的与要求

(1) 理解继承的定义；

(2) 掌握子类的定义要求

(3) 掌握多态性的概念及用法；

(4) 掌握抽象类的定义及用途；

(5) 掌握类中4个成员访问权限修饰符的用途；

(6) 掌握抽象类的定义方法及用途；

(7)掌握Object类的用途及常用API；

(8) 掌握ArrayList类的定义方法及用法；

(9) 掌握枚举类定义方法及用途。

2、实验内容和步骤

实验1： 导入第5章示例程序，测试并进行代码注释。

测试程序1：

? 在elipse IDE中编辑、调试、运行程序5-1 （教材152页-153页） ；

? 掌握子类的定义及用法；

? 结合程序运行结果，理解并总结OO风格程序构造特点，理解Employee和Manager类的关系子类的用途，并在代码中添加注释。

package inheritance;

/**
 * This program demonstrates inheritance.
 * 
 * @version 1.21 2004-02-21
 * @author Cay Horstmann
 */
public class ManagerTest {
    public static void main(String[] args) {
        // construct a Manager object
        Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);// 执行完该行之后bonus为0
        boss.setBonus(5000);//set调用更改器方法将bonus改为5000

        Employee[] staff = new Employee[3];//定义一个Employee类，new后使用构造器方法并将该数组初始化为3。

        // fill the staff array with Manager and Employee objects

        staff[0] = boss;//boss是Employee类的子类对象。
        staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
        staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);
//staff也是Employee类。
        // print out information about all Employee objects
        for (Employee e : staff)
            System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());//使用get调用访问器 方法
    }
}

 

package inheritance;

public class Manager extends Employee
{
   private double bonus;

   /**
    * @param name the employee‘s name
    * @param salary the salary
    * @param year the hire year
    * @param month the hire month
    * @param day the hire day
    */
   public Manager(String name, double salary, int year, int month, int day)
   {
      super(name, salary, year, month, day);
      bonus = 0;
   }

   public double getSalary()
   {
      double baseSalary = super.getSalary();
      return baseSalary + bonus;
   }

   public void setBonus(double b)
   {
      bonus = b;
   }
}

package inheritance;

/**
 * This program demonstrates inheritance.
 * @version 1.21 2004-02-21
 * @author Cay Horstmann
 */
public class ManagerTest
{
   public static void main(String[] args)
   {
      // construct a Manager object
      Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      boss.setBonus(5000);

      Employee[] staff = new Employee[3];

      // fill the staff array with Manager and Employee objects

      staff[0] = boss;
      staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
      staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);

      // print out information about all Employee objects
      for (Employee e : staff)
         System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
   }
}

运行结果：

测试程序2：

? 编辑、编译、调试运行教材PersonTest程序（教材163页-165页)；

? 掌握超类的定义及其使用要求；

? 掌握利用超类扩展子类的要求；

? 在程序中相关代码处添加新知识的注释。

 

/**
 * This program demonstrates abstract classes.
 * @version 1.01 2004-02-21
 * @author Cay Horstmann
 */
public class PersonTest//主类
{
   public static void main(String[] args)
   {
      Person[] people = new Person[2];

      //用Employee类和Student类填充people数组
      people[0] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
      people[1] = new Student("Maria Morris", "computer science");

      //打印出所有person类的名字和其他描述
      for (Person p : people)
         System.out.println(p.getName() + ", " + p.getDescription());
   }
}

public abstract class Person//抽象类：Person
{
   public abstract String getDescription();
   private String name;//传建一个私有属性

   public Person(String name)//构造器
   {
      this.name = name;
   }

   public String getName()//访问器
   {
      return name;
   }
}

public class Student extends Person//子类：Student类继承Person类
{
   private String major;//创建一个私有属性major

   /**
    * @param nama the student‘s name
    * @param major the student‘s major
    */
   public Student(String name, String major)//构造器
   {
    
      super(name);//子类直接调用超类中的name属性
      this.major = major;
   }

   public String getDescription()//访问器
   {
      return "a student majoring in " + major;
   }
}
import java.time.*;

public class Employee extends Person//子类：Employee类继承Person类
{
   private double salary;
   private LocalDate hireDay;
//两个私有属性
   public Employee(String name, double salary, int year, int month, int day)//构造器
   {
      super(name);//子类直接调用超类中的name
      this.salary = salary;
      hireDay = LocalDate.of(year, month, day);
   }

   public double getSalary()
   {
      return salary;
   }

   public LocalDate getHireDay()
   {
      return hireDay;
   }

   public String getDescription()
   {
      return String.format("an employee with a salary of $%.2f", salary);
   }
//访问器
   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }//定义两个局部变量
}

运行结果：

测试程序3：

? 编辑、编译、调试运行教材程序5-8、5-9、5-10，结合程序运行结果理解程序（教材174页-177页）；

? 掌握Object类的定义及用法；

? 在程序中相关代码处添加新知识的注释。

package equals;

/**
 * This program demonstrates the equals method.
 * @version 1.12 2012-01-26
 * @author Cay Horstmann
 */
public class EqualsTest
{
   public static void main(String[] args)
   {
      Employee alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee alice2 = alice1;
      Employee alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
      Employee bob = new Employee("Bob Brandson", 50000, 1989, 10, 1);

      System.out.println("alice1 == alice2: " + (alice1 == alice2));

      System.out.println("alice1 == alice3: " + (alice1 == alice3));

      System.out.println("alice1.equals(alice3): " + alice1.equals(alice3));

      System.out.println("alice1.equals(bob): " + alice1.equals(bob));

      System.out.println("bob.toString(): " + bob);

      Manager carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
      boss.setBonus(5000);
      System.out.println("boss.toString(): " + boss);
      System.out.println("carl.equals(boss): " + carl.equals(boss));
      System.out.println("alice1.hashCode(): " + alice1.hashCode());
      System.out.println("alice3.hashCode(): " + alice3.hashCode());
      System.out.println("bob.hashCode(): " + bob.hashCode());
      System.out.println("carl.hashCode(): " + carl.hashCode());
   }
}

package equals;

public class Manager extends Employee
{
   private double bonus;

   public Manager(String name, double salary, int year, int month, int day)
   {
      super(name, salary, year, month, day);
      bonus = 0;
   }

   public double getSalary()
   {
      double baseSalary = super.getSalary();
      return baseSalary + bonus;
   }

   public void setBonus(double bonus)
   {
      this.bonus = bonus;
   }

   public boolean equals(Object otherObject)
   {
      if (!super.equals(otherObject)) return false;
      Manager other = (Manager) otherObject;
      // 检查这个和其他属于同一个类
      return bonus == other.bonus;
   }

   public int hashCode()
   {
      return java.util.Objects.hash(super.hashCode(), bonus);
   }

   public String toString()
   {
      return super.toString() + "[bonus=" + bonus + "]";
   }
}

package equals;

import java.time.*;
import java.util.Objects;

public class Employee
{
   private String name;
   private double salary;
   private LocalDate hireDay;

   public Employee(String name, double salary, int year, int month, int day)
   {
      this.name = name;
      this.salary = salary;
      hireDay = LocalDate.of(year, month, day);
   }

   public String getName()
   {
      return name;
   }

   public double getSalary()
   {
      return salary;
   }

   public LocalDate getHireDay()
   {
      return hireDay;
   }

   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }

   public boolean equals(Object otherObject)
   {
      // 快速检查对象是否相同
//       这里获得一个对象参数，第一个if语句判断两个引用是否是同一个，如果是那么这两个对象肯定相等
      if (this == otherObject) return true;

      // 如果显式参数为空，则必须返回false
      if (otherObject == null) return false;


      if (getClass() != otherObject.getClass()) return false;

     //    父类引用子类的对象的出现，然后再判断对象的属性是否相同
      Employee other = (Employee) otherObject;

      // 测试字段是否具有相同的值
      return Objects.equals(name, other.name) && salary == other.salary && Objects.equals(hireDay, other.hireDay);
   }

   public int hashCode()

   {
      return Objects.hash(name, salary, hireDay); 
   }

   public String toString()
   {
      return getClass().getName() + "[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay
            + "]";
   }
}

运行结果：

测试程序4：

? 在elipse IDE中调试运行程序5-11（教材182页），结合程序运行结果理解程序；

? 掌握ArrayList类的定义及用法；

? 在程序中相关代码处添加新知识的注释。

package arrayList;

import java.util.*;

/**
 * This program demonstrates the ArrayList class.
 * @version 1.11 2012-01-26
 * @author Cay Horstmann
 */
public class ArrayListTest
{
   public static void main(String[] args)
   {
      // 用三个Employee对象填充staff数组列表
      ArrayList<Employee> staff = new ArrayList<>();

      staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15));
      staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1));
      staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15));

      // 把每个人的薪水提高5%
      for (Employee e : staff)
         e.raiseSalary(5);

      // 打印所有Employee对象的信息
      for (Employee e : staff)
         System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="
               + e.getHireDay());
   }
}

//employee类：
package arrayList;

import java.time.*;

public class Employee
{
   private String name;
   private double salary;
   private LocalDate hireDay;

   public Employee(String name, double salary, int year, int month, int day)
   {
      this.name = name;
      this.salary = salary;
      hireDay = LocalDate.of(year, month, day);
   }

   public String getName()
   {
      return name;
   }

   public double getSalary()
   {
      return salary;
   }

   public LocalDate getHireDay()
   {
      return hireDay;
   }

   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }
}

运行结果：

测试程序5：

? 编辑、编译、调试运行程序5-12（教材189页），结合运行结果理解程序；

? 掌握枚举类的定义及用法；

? 在程序中相关代码处添加新知识的注释。

package enums;

import java.util.*;

/**
 * This program demonstrates enumerated types.
 * @version 1.0 2004-05-24
 * @author Cay Horstmann
 */
public class EnumTest
{  
   public static void main(String[] args)
   {  
      Scanner in = new Scanner(System.in);
      System.out.print("Enter a size: (SMALL, MEDIUM, LARGE, EXTRA_LARGE) ");
      String input = in.next().toUpperCase();
      Size size = Enum.valueOf(Size.class, input);
      System.out.println("size=" + size);
      System.out.println("abbreviation=" + size.getAbbreviation());
      if (size == Size.EXTRA_LARGE)//判断语句
         System.out.println("Good job--you paid attention to the _.");      
   }
}

enum Size
{
   SMALL("S"), MEDIUM("M"), LARGE("L"), EXTRA_LARGE("XL");

   private Size(String abbreviation) { this.abbreviation = abbreviation; }
   public String getAbbreviation() { return abbreviation; }

   private String abbreviation;
}

运行结果;

 

实验2：编程练习1

? 定义抽象类Shape：

属性：不可变常量double PI，值为3.14；

方法：public double getPerimeter()；public double getArea())。

? 让Rectangle与Circle继承自Shape类。

? 编写double sumAllArea方法输出形状数组中的面积和和double sumAllPerimeter方法输出形状数组中的周长和。 

? main方法中

1）输入整型值n，然后建立n个不同的形状。如果输入rect，则再输入长和宽。如果输入cir，则再输入半径。
2） 然后输出所有的形状的周长之和，面积之和。并将所有的形状信息以样例的格式输出。
3） 最后输出每个形状的类型与父类型，使用类似shape.getClass()(获得类型)，shape.getClass().getSuperclass()(获得父类型);

思考sumAllArea和sumAllPerimeter方法放在哪个类中更合适？

输入样例:

3

rect

1 1

rect

2 2

cir

1

输出样例:

18.28

8.14

18.28

8.14

[Rectangle [width=1, length=1], Rectangle [width=2, length=2], Circle [radius=1]]

class Rectangle,class Shape

class Rectangle,class Shape

class Circle,class Shape

实验一代码及结果如下：

主类：

package demo1;

import java.util.Scanner;

public class Text1 {
    public static void main(String[] args) {
        // TODO 自动生成的方法存
        @SuppressWarnings("resource")
        Scanner in = new Scanner(System.in);
        String rect = "rect";
        String cir = "cir";
        System.out.println("请输入不同的形状个数:");
        int n = in.nextInt();
        shape[] num = new shape[n];
        for (int i = 0; i < n; i++) {
            System.out.println("请输入形状类型 (rect or cir):");
            String input = in.next();
            if (input.equals(rect)) {
                System.out.println("长和宽");
                double length = in.nextDouble();
                double width = in.nextDouble();
                System.out.println("Rectangle[" + "length:" + length + "  width:" + width + "]");
                num[i] = new Rectangle(width, length);
            }
            if (input.equals(cir)) {
                System.out.println("半径    ");
                double radius = in.nextDouble();
                System.out.println("Circle[" + "radius:" + radius + "]");
                num[i] = new Circle(radius);
            }
        }
        Text1 c = new Text1();
        System.out.println("求和");
        System.out.println(c.sumAllPerimeter(num));
        System.out.println(c.sumAllArea(num));

        for (shape s : num) {
            System.out.println(s.getClass() + "," + s.getClass().getSuperclass());
        }
    }

    public double sumAllArea(shape score[]) {
        double sum = 0;
        for (int i = 0; i < score.length; i++)
            sum += score[i].getArea();
        return sum;
    }

    public double sumAllPerimeter(shape score[]) {
        double sum = 0;
        for (int i = 0; i < score.length; i++)
            sum += score[i].getPerimeter();
        return sum;
    }

}

抽象类Shape：

public abstract class shape {
    double PI = 3.14;

    abstract double getPerimeter();

    abstract double getArea();
}

circle类：

public  class Circle extends shape {

    
    private double radius;
    public Circle(double radius) {
        
    }
     public double getPerimeter()
        {
            double Perimeter=2*PI*radius;
            return Perimeter;
        }
        public double getArea()
        {
            double Area=PI*radius*radius;
            return Area;
        }
    }
 

Rectangle类：

public class Rectangle extends shape {

    private double length;
    private double width;

    public Rectangle(double width, double length) {
        
        this.length = length;
        this.width = width;
    }
    
public double getPerimeter() {
    double Perimeter=2*(length + width);
        return  Perimeter ;
    }

    
    public double getArea() {
        double Area= length * width;
        return Area;
    }

}

运行结果：

 

实验3： 编程练习2

编制一个程序，将身份证号.txt 中的信息读入到内存中，输入一个身份证号或姓名，查询显示查询对象的姓名、身份证号、年龄、性别和出生地。

程序如下：

 

package demo2;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Scanner;

public class Demo2 {

    private static ArrayList<Student> studentlist;

    public static void main(String[] args) {
        studentlist = new ArrayList<>();
        
        @SuppressWarnings("resource")
        Scanner scanner = new Scanner(System.in);

        File file = new File("D:\\身份证号\\身份证号.txt");

        try {

            FileInputStream fis = new FileInputStream(file);

            @SuppressWarnings("resource")
            BufferedReader in = new BufferedReader(new InputStreamReader(fis));
            String temp = null;
            while ((temp = in.readLine()) != null) {
                
                @SuppressWarnings("resource")
                Scanner linescanner = new Scanner(temp);

                linescanner.useDelimiter(" ");
                String name = linescanner.next();
                String number = linescanner.next();
                String sex = linescanner.next();
                String year = linescanner.next();
                String province = linescanner.nextLine();
                Student student = new Student();
                student.setName(name);
                student.setNumber(number);
                student.setSex(sex);
                student.setYear(year);
                student.setProvince(province);
                studentlist.add(student);

            }

        } catch (FileNotFoundException e) {

            System.out.println("所找信息文件找不到");
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            System.out.println("所找信息文件读取错误");
            e.printStackTrace();
        }

        boolean isTrue = true;
        while (isTrue) {

            System.out.println("欢迎来到信息查询系统,请选择你的操作");
            System.out.println("1.按姓名查询");
            System.out.println("2.按身份证号查询");
            System.out.println("3.退出");
            int nextInt = scanner.nextInt();
            switch (nextInt) {
            case 1:
                System.out.println("请输入姓名");
                String studentname = scanner.next();
                int nameint = findStudentByname(studentname);
                if (nameint != -1) {
                    System.out.println("查找信息为：身份证号:" + studentlist.get(nameint).getNumber() + "    姓名:"
                            + studentlist.get(nameint).getName() + "    性别:" + studentlist.get(nameint).getSex()
                            + "    年龄:" + studentlist.get(nameint).getYear() + "  地址:"
                            + studentlist.get(nameint).getProvince());

                } else {
                    System.out.println("不存在该人");
                }
                break;
            case 2:
                System.out.println("请输入身份证号");
                String studentid = scanner.next();
                int idint = findStudentByid(studentid);
                if (idint != -1) {
                    System.out.println("查找信息为：身份证号:" + studentlist.get(idint).getNumber() + "    姓名:"
                            + studentlist.get(idint).getName() + "    性别:" + studentlist.get(idint).getSex() + "    年龄:"
                            + studentlist.get(idint).getYear() + "   地址:" + studentlist.get(idint).getProvince());

                } else {
                    System.out.println("不存在该人");
                }
                break;
            case 3:
                isTrue = false;
                System.out.println("程序已退出!");
                break;
            default:
                System.out.println("输入有误");
            }
        }
    }

    public static int findStudentByname(String name) {
        int flag = -1;

        for (int i = 0; i < studentlist.size(); i++) {
            if (studentlist.get(i).getName().equals(name)) {
                flag = i;
            }
        }
        return flag;

    }

    public static int findStudentByid(String id) {
        int flag = -1;

        for (int i = 0; i < studentlist.size(); i++) {
            if (studentlist.get(i).getId().equals(id)) {
                flag = i;
            }
        }
        return flag;

    }
}

 

封装类如下所示：

public class Student {
    private String name;
    private String id;
    private String number;
    private String sex;
    private String year;
    private String province;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;

    }
    public String getNumber() {
        // TODO 自动生成的方法存根
        return number;
    }
    public void setNumber(String number) {
        this.number = number;

    }

    public String getSex() {
        // TODO 自动生成的方法存根
        return sex;
    }
    public void setSex(String sex) {
        // TODO 自动生成的方法存根
        this.sex = sex;

    }
    public String getYear() {
        // TODO 自动生成的方法存根
        return year;
    }

    public void setYear(String year) {
        // TODO 自动生成的方法存根
        this.year = year;

    }
    public String getProvince() {
        // TODO 自动生成的方法存根
        return province;
    }

    public void setProvince(String province) {
        // TODO 自动生成的方法存根
        this.province = province;

    }
}

运行结果如下：

实验总结：通过本次实验二让我更加明确了封装的概念，以及读取文件的操作，通过实验一让我更进一步的理解了继承的概念，在此次代码注释过程中，我发现了自己的不足之处在于，对有些代码还是不太清楚其语义，以及其含义，上次老师讲授代码的含义时，对我帮助极大，希望老师还可以选择讲一些代码的作用。这样在我自己学习时，就可结合老师的讲授去理解。