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

                                               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：

class Parent {
    private String p1 = "这是Parent的私有属性";
    public String p2 = "这是Parent的公有属性";
    protected String p3 = "这是Parent受保护的属性";
    String p4 = "这是Parent的默认属性";
    private void pMethod1() {
        System.out.println("我是Parent用private修饰符修饰的方法");
    }
    public void pMethod2() {
        System.out.println("我是Parent用public修饰符修饰的方法");
    }
    protected void pMethod3() {
        System.out.println("我是Parent用protected修饰符修饰的方法");
    }
    void pMethod4() {
        System.out.println("我是Parent无修饰符修饰的方法");
    }
}
class Son extends Parent{
    private String s1 = "这是Son的私有属性";
    public String s2 = "这是Son的公有属性";
    protected String s3 = "这是Son受保护的属性";
    String s4 = "这是Son的默认属性";
    public void sMethod1() {
        System.out.println("...");//分别尝试显示Parent类的p1、p2、p3、p4值
        System.out.println("我是Son用public修饰符修饰的方法");
    }
    private void sMethod2() {
        System.out.println("我是Son用private修饰符修饰的方法");
    }
    protected void sMethod() {
        System.out.println("我是Son用protected修饰符修饰的方法");
    }
    void sMethod4() {
        System.out.println("我是Son无修饰符修饰的方法");
    }    
}
public class Demo {
    public static void main(String[] args) {
        Parent parent = new Parent();
        Son son = new Son();
        Parent   pMethod3= new Son ();

        ((Son) pMethod3).sMethod1();

        ((Son) pMethod3).pMethod3();

        ((Son) pMethod3).sMethod4();

        pMethod3.pMethod2();

        pMethod3.pMethod3();

        pMethod3.pMethod4();

     

        System.out.println(pMethod3.p2);

        System.out.println(pMethod3.p3);

        System.out.println(pMethod3.p4); 
    }
}

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：

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);

        // TODO Auto-generated constructor stub

         bonus = 0;

    }

    public void setBonus(double bonus) {

        this.bonus = bonus;

    }

    @Override

    public double getSalary() {

        // TODO Auto-generated method stub

        double baseSalary= super.getSalary();

        return baseSalary+bonus;

    }

    @Override

    public boolean equals(Object otherObject) {

        // TODO Auto-generated method stub

        if(!super.equals(otherObject)) return false;

        Manager other=(Manager)otherObject;

        return bonus==other.bonus;

    }

    @Override

    public int hashCode() {

        // TODO Auto-generated method stub

        return super.hashCode()+17*new Double(bonus).hashCode();

    }

    @Override

    public String toString() {

        // TODO Auto-generated method stub

        return super.toString()+"[bonus="+bonus+"]";

    }

  

}

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：

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)
   {
      // fill the staff array list with three Employee objects
      ArrayList<Employee> staff = new ArrayList<Employee>();

      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));

      // raise everyone's salary by 5%
      for (Employee e : staff)
         e.raiseSalary(5);

      // print out information about all Employee objects
      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;
   }
}

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。

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)

   {

      // fill the staff array list with three Employee objects

      ArrayList<Employee> staff = new ArrayList<Employee>();  //声明和构造一个保存Employee对象的数组列表

      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

      staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1));

      staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15));

      staff.remove(1);  //从数组列表中删除元素

      int n = staff.size();

      System.out.println(n);

     System.out.println(staff.get(0)!=staff.get(1));

      // raise everyone's salary by 5%

      for (Employee e : staff)

         e.raiseSalary(5);

      // print out information about all Employee objects

      for (Employee e : staff)

         System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="

            + e.getHireDay());

   }

}

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：

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);//字符串转换为大写
      System.out.print("Enter a size: (SMALL, MEDIUM, LARGE, EXTRA_LARGE) ");
      String input = in.next().toUpperCase();
      Size size = Enum.valueOf(Size.class, input);//静态values方法返回枚举的所有值的数组
      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：

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。

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)
   {  
      var 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;
}

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：

package CLD;

public class TestVarArgus {  

    public static void dealArray(int... intArray){  

        for (int i : intArray)  

            System.out.print(i +" ");  

           

        System.out.println();  

    }        

    public static void main(String args[]){  

        dealArray();  

        dealArray(1);  

        dealArray(1, 2, 3);  

    }  

}

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：

public class Demo {

    public static void main(String[] args) {

        Son son = new Son();

        son.method();

    }

}

class Parent {

    Parent() {

        System.out.println("Parent's Constructor without parameter");

    }

    Parent(boolean b) {

        System.out.println("Parent's Constructor with a boolean parameter");

    }

    public void method() {

        System.out.println("Parent's method()");

    }

}

class Son extends Parent {

    Son(){

         super(false);

        System.out.println("Son's Constructor without parameter");

        System.out.println("Son's method()");        super.method();

        }

    }

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。