实验七 继承附加实验

实验七继承附加实验

实验时间 2018-10-11

1、实验目的与要求

（1）进一步理解4个成员访问权限修饰符的用途；

（2）掌握Object类的常用API用法；

（3）掌握ArrayList类用法与常用API；

（4）掌握枚举类使用方法；

（5）结合本章知识，理解继承与多态性两个面向对象程序设计特征，并体会其优点；

（6）熟练掌握Java语言中基于类、继承技术构造程序的语法知识（ch1-ch5）；

（7）利用已掌握Java语言程序设计知识，学习设计开发含有1个主类、2个以上用户自定义类的应用程序。

2、实验内容和步骤

实验1  补充以下程序中主类内main方法体，以验证四种权限修饰符的用法。

public class TEST1 {

       private String t1 = "这是TEST1的私有属性";

       public String t2 = "这是TEST1的公有属性";

       protected String t3 = "这是TEST1受保护的属性";

       String t4 = "这是TEST1的默认属性";

       private void tese1() {

              System.out.println("我是TEST1用private修饰符修饰的方法");

       }

       public void tese2() {

              System.out.println("我是TEST1用public修饰符修饰的方法");

       }

       protected void tese3() {

              System.out.println("我是TEST1用protected修饰符修饰的方法");

       }

       void tese4() {

              System.out.println("我是TEST1无修饰符修饰的方法");

       }

}

public class TEST2   extends TEST1{

       private String e1 = "这是TEST2的私有属性";

       public String e2 = "这是TEST2的公有属性";

       protected String e3 = "这是TEST2受保护的属性";

       String e4 = "这是TEST2的默认属性";

       public void demo1() {

              System.out.println("我是TEST2用public修饰符修饰的方法");

       }

       private void demo2() {

              System.out.println("我是TEST2用private修饰符修饰的方法");

       }

       protected void demo3() {

              System.out.println("我是TEST2用protected修饰符修饰的方法");

       }

       void demo4() {

              System.out.println("我是TEST2无修饰符修饰的方法");

       }

}

public class Main {

       public static void main(String[] args)   {

              TEST2 test2 = new TEST2();

              /*以下设计代码分别调用 demo1 demo2 demo3 demo4 test1 test2 test3 test4方法和t1 t2 t3 t3 e1 e2 e3 e4属性，结合程序运行结果理解继承和权限修饰符的用法与区别*/

       }

}

实验2  第五章测试程序反思，继承知识总结。

测试程序1：

Ÿ   编辑、编译、调试运行教材程序5-8、5-9、5-10（教材174页-177页）；

Ÿ   结合程序运行结果，理解程序代码，掌握Object类的定义及用法；

package equals;

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

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

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

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

   public double getSalary()
   {
      return salary;
   }          //访问器


   public LocalDate getHireDay()
   {
      return hireDay;
   }          //访问器

   public void raiseSalary(double byPercent)
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }          //完成涨工资的计算

   public boolean equals(Object otherObject)
   {
      //快速测试，看看这些对象是否相同      
      if (this == otherObject) return true;

      //  如果显式参数为空，则必须返回false

      if (otherObject == null) return false;

      // 如果类不匹配，它们就不能相等
      if (getClass() != otherObject.getClass()) return false;

      //  现在我们知道otherObject是一个非空雇员
      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()   //hashcode返回散列码
   {
      return Objects.hash(name, salary, hireDay); 
   }

   public String toString()    //返回类对象的状态信息
   {
      return getClass().getName() + "[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay
            + "]";
   }
}

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;
      //super.equals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 + "]";
   }
}

测试程序2：

Ÿ   编辑、编译、调试运行教材程序5-11（教材182页）；

Ÿ   结合程序运行结果，理解程序代码，掌握ArrayList类的定义及用法；

代码如下

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));

      // 把每个人的工资提升百分之五
      for (Employee e : staff)
         e.raiseSalary(5);

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

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;
   }
}

测试程序3：

Ÿ   编辑、编译、调试运行程序5-12（教材189页）；

Ÿ   结合运行结果，理解程序代码，掌握枚举类的定义及用法；

代码如下

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)
         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;
}

实验3：采用个人账号登录https://pintia.cn/，完成《2018秋季西北师范大学面向对象程序设计（Java）（ch1-ch5）测试题2》，测试时间60分钟；

实验4: 课后完成实验3未完成的测试内容。

实验总结：这次附加实验在上次实验的基础上，对第五章的内容有了更加深入的了解，尤其是对于四种权限修饰符的使用。此外掌握Object类的常用API用法，掌握ArrayList类用法与和枚举类使用方法；

有所提高，仍需努力。