201871010101-陈来弟《面向对象程序设计（java）》第七周学习总结

项目	内容
《面向对象程序设计（java）》	https://www.cnblogs.com/nwnu-daizh/
这个作业的要求在哪里	https://www.cnblogs.com/nwnu-daizh/p/11654436.html
作业学习目标	掌握四种访问权限修饰符的使用特点；掌握Object类的用途及常用API；掌握ArrayList类的定义方法及用途；掌握枚举类定义方法及用途；结合本章实验内容，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。

实验内容和步骤

实验1：（20分）

在“System.out.println(...);”语句处按注释要求设计代码替换...，观察代码录入中IDE提示，以验证四种权限修饰符的用法。

程序代码如下：

 1 class Parent {
 2     private String p1 = "这是Parent的私有属性";
 3     public String p2 = "这是Parent的公有属性";
 4     protected String p3 = "这是Parent受保护的属性";
 5     String p4 = "这是Parent的默认属性";
 6     private void pMethod1() {
 7         System.out.println("我是Parent用private修饰符修饰的方法");
 8     }
 9     public void pMethod2() {
10         System.out.println("我是Parent用public修饰符修饰的方法");
11     }
12     protected void pMethod3() {
13         System.out.println("我是Parent用protected修饰符修饰的方法");
14     }
15     void pMethod4() {
16         System.out.println("我是Parent无修饰符修饰的方法");
17     }
18 }
19 class Son extends Parent{
20     private String s1 = "这是Son的私有属性";
21     public String s2 = "这是Son的公有属性";
22     protected String s3 = "这是Son受保护的属性";
23     String s4 = "这是Son的默认属性";
24     public void sMethod1() {
25         System.out.println("...");//分别尝试显示Parent类的p1、p2、p3、p4值
26         System.out.println("我是Son用public修饰符修饰的方法");
27     }
28     private void sMethod2() {
29         System.out.println("我是Son用private修饰符修饰的方法");
30     }
31     protected void sMethod() {
32         System.out.println("我是Son用protected修饰符修饰的方法");
33     }
34     void sMethod4() {
35         System.out.println("我是Son无修饰符修饰的方法");
36     }    
37 }
38 public class Demo {
39     public static void main(String[] args) {
40         Parent parent = new Parent();
41         Son son = new Son();
42         Parent   pMethod3= new Son ();
43 
44         ((Son) pMethod3).sMethod1();
45 
46         ((Son) pMethod3).pMethod3();
47 
48         ((Son) pMethod3).sMethod4();
49 
50         pMethod3.pMethod2();
51 
52         pMethod3.pMethod3();
53 
54         pMethod3.pMethod4();
55 
56      
57 
58         System.out.println(pMethod3.p2);
59 
60         System.out.println(pMethod3.p3);
61 
62         System.out.println(pMethod3.p4); 
63     }
64 }

运行结果：

实验2：导入第5章以下示例程序，测试并进行代码注释。

测试程序1：

l 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）；

l 删除程序中Employee类、Manager类中的equals()、hasCode()、toString()方法，背录删除方法，在代码录入中理解类中重写Object父类方法的技术要点。

5-8程序代码如下：

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());
   }
}

5-9程序代码如下：

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)
   {
      // a quick test to see if the objects are identical
      if (this == otherObject) return true;

      // must return false if the explicit parameter is null
      if (otherObject == null) return false;

      // if the classes don't match, they can't be equal
      if (getClass() != otherObject.getClass()) return false;

      // now we know otherObject is a non-null Employee
      var other = (Employee) otherObject;

      // test whether the fields have identical values
      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 + "]";
   }
}

5-10程序代码如下：

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;
      var other = (Manager) otherObject;
      // super.equals checked that this and other belong to the same class
      return bonus == other.bonus;
   }

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

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

三个程序运行结果：

删除程序中Employee类、Manager类中的equals()、hasCode()、toString()方法，背录删除方法，在代码录入中理解类中重写Object父类方法的技术要点。

Manager：

 1 public class Manager extends Employee
 2 
 3 {
 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 
11         // TODO Auto-generated constructor stub
12 
13          bonus = 0;
14 
15     }
16 
17     public void setBonus(double bonus) {
18 
19         this.bonus = bonus;
20 
21     }
22 
23     @Override
24 
25     public double getSalary() {
26 
27         // TODO Auto-generated method stub
28 
29         double baseSalary= super.getSalary();
30 
31         return baseSalary+bonus;
32 
33     }
34 
35     @Override
36 
37     public boolean equals(Object otherObject) {
38 
39         // TODO Auto-generated method stub
40 
41         if(!super.equals(otherObject)) return false;
42 
43         Manager other=(Manager)otherObject;
44 
45         return bonus==other.bonus;
46 
47     }
48 
49     @Override
50 
51     public int hashCode() {
52 
53         // TODO Auto-generated method stub
54 
55         return super.hashCode()+17*new Double(bonus).hashCode();
56 
57     }
58 
59     @Override
60 
61     public String toString() {
62 
63         // TODO Auto-generated method stub
64 
65         return super.toString()+"[bonus="+bonus+"]";
66 
67     }
68 
69   
70 
71 }

Employee：

import java.time.*;

import java.util.Objects;

 

public class Employee

{

   private String name;    //实例域定义

   private double salary;

   private LocalDate hireDay;

 

   public Employee(String name, double salary, int year, int month, int day)//构造器定义

   {

      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;

}

 

 

@Override

public boolean equals(Object otherObject) {

    // TODO Auto-generated method stub

    if(this==otherObject) return true;

    if(this==null) return false;

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

    Employee other=(Employee)otherObject;

    return Objects.equals(name,other.name)&&salary == other.salary&&Objects.equals(hireDay,other.hireDay);

}

@Override

public int hashCode() {

    // TODO Auto-generated method stub

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

}

 

@Override

public String toString() {

    // TODO Auto-generated method stub

    return getClass().getName()+"[name="+name+",salary="+salary+",hireday="+hireDay+"]";

}
}

运行结果：

Object类存储在java.lang包中，是所有java类(Object类除外)的终极父类。当然，数组也继承了Object类。然而，接口是不继承Object类的，“Object类不作为接口的父类”。java的任何类都继承了这些函数，并且可以覆盖不被final修饰的函数。例如，没有final修饰的toString()函数可以被覆盖，但是final wait()函数就不行。Java也没有强制声明“继承Object类”。如果这样的话，就不能继承除Object类之外别的类了，因为java不支持多继承。然而，即使不声明出来，也会默认继承了Object类，

测试程序2：

l 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；

l 掌握ArrayList类的定义及用法；

l 在程序中相关代码处添加新知识的注释；

5-11代码：

 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       // fill the staff array list with three Employee objects
15       ArrayList<Employee> staff = new ArrayList<Employee>();
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       // raise everyone's salary by 5%
22       for (Employee e : staff)
23          e.raiseSalary(5);
24 
25       // print out information about all Employee objects
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 }

运行结果：

l 设计适当的代码，测试ArrayList类的set()、get()、remove()、size()等方法的用法。

 1 package arrayList;
 2 
 3 import java.util.*;
 4 
 5 /**
 6 
 7  * This program demonstrates the ArrayList class.
 8 
 9  * @version 1.11 2012-01-26
10 
11  * @author Cay Horstmann
12 
13  */
14 
15 public class ArrayListTest
16 
17 {
18 
19    public static void main(String[] args)
20 
21    {
22 
23       // fill the staff array list with three Employee objects
24 
25       ArrayList<Employee> staff = new ArrayList<Employee>();  //声明和构造一个保存Employee对象的数组列表
26 
27       staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15));//使用add方法将元素添加到数组列表中
28 
29       staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1));
30 
31       staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15));
32 
33       staff.remove(1);  //从数组列表中删除元素
34 
35       int n = staff.size();
36 
37       System.out.println(n);
38 
39      System.out.println(staff.get(0)!=staff.get(1));
40 
41       // raise everyone's salary by 5%
42 
43       for (Employee e : staff)
44 
45          e.raiseSalary(5);
46 
47       // print out information about all Employee objects
48 
49       for (Employee e : staff)
50 
51          System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="
52 
53             + e.getHireDay());
54 
55    }
56 
57 }

运行结果：

ArrayList是集合的一种实现，实现了接口List，List接口继承了Collection接口。Collection是所有集合类的父类。ArrayList使用非常广泛，不论是数据库表查询，excel导入解析，还是网站数据爬取都需要使用到，了解ArrayList原理及使用方法显得非常重要。

测试程序3：

l 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；

l 掌握枚举类的定义及用法；

l 在程序中相关代码处添加新知识的注释；

5-12代码：

 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);//字符串转换为大写
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);//静态values方法返回枚举的所有值的数组
18       System.out.println("size=" + size);
19       System.out.println("abbreviation=" + size.getAbbreviation());
20       if (size == Size.EXTRA_LARGE)//判断语句
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 }

运行结果：

l 删除程序中Size枚举类，背录删除代码，在代码录入中掌握枚举类的定义要求。

 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       var 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 }

运行结果：

java.util.EnumSet和java.util.EnumMap是两个枚举集合。EnumSet保证集合中的元素不重复；EnumMap中的key是enum类型，而value则可以是任意类型。

测试程序4：录入以下代码，结合程序运行结果了解方法的可变参数用法

代码如下：

 1 package CLD;
 2 
 3 public class TestVarArgus {  
 4 
 5     public static void dealArray(int... intArray){  
 6 
 7         for (int i : intArray)  
 8 
 9             System.out.print(i +" ");  
10 
11            
12 
13         System.out.println();  
14 
15     }        
16 
17     public static void main(String args[]){  
18 
19         dealArray();  
20 
21         dealArray(1);  
22 
23         dealArray(1, 2, 3);  
24 
25     }  
26 
27 }

运行结果：

实验:3：编程练习：参照输出样例补全程序，使程序输出结果与输出样例一致。

代码：

 1 public class Demo {
 2 
 3     public static void main(String[] args) {
 4 
 5         Son son = new Son();
 6 
 7         son.method();
 8 
 9     }
10 
11 }
12 
13 class Parent {
14 
15     Parent() {
16 
17         System.out.println("Parent's Constructor without parameter");
18 
19     }
20 
21     Parent(boolean b) {
22 
23         System.out.println("Parent's Constructor with a boolean parameter");
24 
25     }
26 
27     public void method() {
28 
29         System.out.println("Parent's method()");
30 
31     }
32 
33 }
34 
35 class Son extends Parent {
36 
37     Son(){
38 
39          super(false);
40 
41         System.out.println("Son's Constructor without parameter");
42 
43         System.out.println("Son's method()");        super.method();
44 
45         }
46 
47     }

运行结果：

三，实验总结：

这周的实验大多都是重复上周的实验所以也没有大的难度，让我在前一次实验的基础上对继承有了进一步的了解，但通过测试发现了很多的问题，希望通过后期的学习可以尝试着独自解决这些问题。

posted @ 2019-10-14 21:52 201871010101-陈来弟阅读(156) 评论(1) 编辑收藏举报

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201871010101-陈来弟《面向对象程序设计（java）》第七周学习总结

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