实验七 继承附加实验

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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*/

       }

}

技术分享图片

实验2  第五章测试程序反思,继承知识总结。

测试程序1:

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

?   结合程序运行结果,理解程序代码,掌握Object类的定义及用法;

技术分享图片

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());
   }
}
 1 package equals;
 2 
 3 public class Manager extends Employee
 4 {
 5    private double bonus;
 6 
 7    public Manager(String name, double salary, int year, int month, int day)
 8    {
 9       super(name, salary, year, month, day);
10       bonus = 0;
11    }
12 
13    public double getSalary()
14    {
15       double baseSalary = super.getSalary();
16       return baseSalary + bonus;
17    }
18 
19    public void setBonus(double bonus)
20    {
21       this.bonus = bonus;
22    }
23 
24    public boolean equals(Object otherObject)
25    {
26       if (!super.equals(otherObject)) return false;
27       Manager other = (Manager) otherObject;
28       //super.equals检查这个和其他属于同一个类
29 return bonus == other.bonus; 30 } 31 32 public int hashCode() 33 { 34 return java.util.Objects.hash(super.hashCode(), bonus); 35 } 36 37 public String toString() 38 { 39 return super.toString() + "[bonus=" + bonus + "]"; 40 } 41 }

 

测试程序2:

?   编辑、编译、调试运行教材程序5-11(教材182页);

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

技术分享图片

代码如下

 1 package arrayList;
 2 
 3 import java.util.*;
 4 
 5 /**
 6  * This program demonstrates the ArrayList class.
 7  * @version 1.11 2012-01-26
 8  * @author Cay Horstmann
 9  */
10 public class ArrayListTest
11 {
12    public static void main(String[] args)
13    {
14       // 用三个Employee对象填充staff数组列表
15 ArrayList<Employee> staff = new ArrayList<>(); 16 17 staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15)); 18 staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1)); 19 staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15)); 20 21 // 把每个人的工资提升百分之五
22 for (Employee e : staff) 23 e.raiseSalary(5); 24 25 // 输出所有雇员对象的信息
26 for (Employee e : staff) 27 System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay=" 28 + e.getHireDay()); 29 } 30 }
 1 package arrayList;
 2 
 3 import java.time.*;
 4 
 5 public class Employee
 6 {
 7    private String name;
 8    private double salary;
 9    private LocalDate hireDay;
10 
11    public Employee(String name, double salary, int year, int month, int day)
12    {
13       this.name = name;
14       this.salary = salary;
15       hireDay = LocalDate.of(year, month, day);
16    }
17 
18    public String getName()
19    {
20       return name;
21    }
22 
23    public double getSalary()
24    {
25       return salary;
26    }
27 
28    public LocalDate getHireDay()
29    {
30       return hireDay;
31    }
32 
33    public void raiseSalary(double byPercent)
34    {
35       double raise = salary * byPercent / 100;
36       salary += raise;
37    }
38 }

 

测试程序3:

?   编辑、编译、调试运行程序5-12(教材189页);

?   结合运行结果,理解程序代码,掌握枚举类的定义及用法;

技术分享图片

代码如下

 1 package enums;
 2 
 3 import java.util.*;
 4 
 5 /**
 6  * This program demonstrates enumerated types.
 7  * @version 1.0 2004-05-24
 8  * @author Cay Horstmann
 9  */
10 public class EnumTest
11 {  
12    public static void main(String[] args)
13    {  
14       Scanner in = new Scanner(System.in);
15       System.out.print("Enter a size: (SMALL, MEDIUM, LARGE, EXTRA_LARGE) ");
16       String input = in.next().toUpperCase();
17       Size size = Enum.valueOf(Size.class, input);
18       System.out.println("size=" + size);
19       System.out.println("abbreviation=" + size.getAbbreviation());
20       if (size == Size.EXTRA_LARGE)
21          System.out.println("Good job--you paid attention to the _.");      
22    }
23 }
24 
25 enum Size
26 {
27    SMALL("S"), MEDIUM("M"), LARGE("L"), EXTRA_LARGE("XL");
28 
29    private Size(String abbreviation) { this.abbreviation = abbreviation; }
30    public String getAbbreviation() { return abbreviation; }
31 
32    private String abbreviation;
33 }

 

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。










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