狄慧201771010104《面向对象程序设计（java）》第七周学习总结

Posted 2021-01-12 dhlll

实验七继承附加实验

实验时间 2018-10-11

一、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。

二、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*/        } }

public class TEST1 {
      private String t1="这是TEST1私有属性";
      public String t2="这是TEST1共有属性";
      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TEST1私有属性";
      public String e2="这是TEST1共有属性";
      protected String e3="这是TEST1受保护的属性";
      String e4="这是TEST1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();
        /*下面分别调用demo1 demo2 demo3 demo4 test1 test2 test3 test4方法和t1 t2 t3 t4 e1 e2 e3 e4属性，理解继承和权限的用法和区别*/
        test.demo1();
        test.demo3();
        test.demo4();    
        test.tese2();
        test.tese3();
        test.tese4();
     
        System.out.println(test.t2);
        System.out.println(test.t3);
        System.out.println(test.t4);
        System.out.println(test.e2);
        System.out.println(test.e3);
        System.out.println(test.e4); 
    }
 
}

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；

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)//加薪
   {
      double raise = salary * byPercent / 100;
      salary += raise;
   }

   public boolean equals(Object otherObject)//相同类（对象 其他对象）
   {
      // a quick test to see if the objects are identical（一个快速检测对象是否一样）
      if (this == otherObject) return true;//如果此对象是其他对象，返回true

      // must return false if the explicit parameter is null（如果明确的参数是空的，必须返回false）
      if (otherObject == null) return false;//如果其他对象是空的，返回false

      // if the classes don‘t match, they can‘t be equal（如果类不能匹配，他们不相同）
      if (getClass() != otherObject.getClass()) return false;//这个类和其他类不匹配

      // now we know otherObject is a non-null Employee（现在我们知道其他类是一个非空的雇员类）
      Employee other = (Employee) otherObject;

      // test whether the fields have identical values（测验是否此域有同样的标准）
      return Objects.equals(name, other.name) && salary == other.salary && Objects.equals(hireDay, other.hireDay);
   }//返回对象相同姓名、薪水、入职时间（这个，另一个）

   public int hashCode()//创建类整型  重新的编码
   {
      return Objects.hash(name, salary, hireDay); 
   }

   public String toString()
   {
      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 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 + "]";
   }
}

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；

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<>();

      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;
   }
}

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；

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。

三、实验总结：

       通过本次实验我学习了Object类的定义及用法，掌握了ArrayList类的定义及用法，也掌握了枚举类的定义及用法，知道了继承最大的特点就是代码重用，让代码变得简洁，让我又积累了优化代码的方法。同时也进一步加深了对4个成员访问权限修饰符的用途的理解。