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  • 201871010106丁宣元 《面向对象程序设计(java)》第七周学习总结

                                                               201871010106-丁宣元 《面向对象程序设计(java)》第七周学习总结

    正文开头:

    项目

    内容

    这个作业属于哪个课程

    https://home.cnblogs.com/u/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

    1. 掌握四种访问权限修饰符的使用特点;
    2. 掌握Object类的用途及常用API;
    3. 掌握ArrayList类的定义方法及用途;
    4. 掌握枚举类定义方法及用途;
    5. 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。

    正文内容:

    实验内容和步骤:

        实验1: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。

          代码:

    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(p2);//p1无法打印,因为是私有属性
            System.out.println(p3);
            System.out.println(p4);//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.pMethod2();    
            parent.pMethod3();
            parent.pMethod4();//分别尝试用parent调用Parent类的方法
            son.sMethod();//用son调用Son类的方法
            son.sMethod1();
            son.sMethod4();//son.sMethod2()是private,只能在son类中使用
        }
    }

      结果:

          注:protected和friendly都只能访问同一个包中的,但protected权限更大些,可访问不同包,但必须是子类继承父类。

        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: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);

                             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。

             1.程序代码

                  5-8EqualsTest.java

    package equals;
    
    /**
     * This program demonstrates the equals method.
     * @version 1.12 2012-01-26
     * @author Cay Horstmann
     */
    public class EqualsTest  //主类
    {
       public static void main(String[] args)
       {
          var alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
          var alice2 = alice1;
          var alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
          var 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);
    
          var carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
          var 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());
       }
    }

        5-9Empolyee.java

    package equals;
    
    import java.time.*;
    import java.util.Objects;
    
    public class Employee //用户自定义类
    {
       private String name; //三个私有属性
       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)//访问器
       {
          double raise = salary * byPercent / 100;
          salary += raise;
       }
    
       public boolean equals(Object otherObject)
       {
          // a quick test to see if the objects are identical 测试几个类是否相同,若引用同一个,则相等
          if (this == otherObject) return true;
    
          // must return false if the explicit parameter is null 若显式参数为空必须返回false
          if (otherObject == null) return false;
    
          // if the classes don't match, they can't be equal若几个类不匹配,则它们不相等
          if (getClass() != otherObject.getClass()) return false;
    
          // now we know otherObject is a non-null Employee  已知otherObject是一个非空雇员
          var other = (Employee) otherObject;
    
          // test whether the fields have identical values 检测是否具有相同的值
          return Objects.equals(name, other.name) 
             && salary == other.salary && Objects.equals(hireDay, other.hireDay);
       }
    
       public int hashCode()//重写hashcode方法,使得相等的两个对象获取的HashCode相等
       {
          return Objects.hash(name, salary, hireDay); 
       }
    
       public String toString()   //其他类型数据转为字符串型的数据
       {
          return getClass().getName() + "[name=" + name + ",salary=" + salary + ",hireDay=" 
             + hireDay + "]";
       }
    }

        5-10Manager.java

    package equals;
    
    public class Manager extends Employee//子类Manager继承Employee
    {
       private double bonus;
    
       public Manager(String name, double salary, int year, int month, int day)
       {
          super(name, salary, year, month, day);//子类调用超类中的属性
          bonus = 0;
       }
    
       public double getSalary()//访问器
       {
          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  使用super.equals检查这个类和其他的是否属于同一个类
          return bonus == other.bonus;
       }
    
       public int hashCode() 
       {
          return java.util.Objects.hash(super.hashCode(), bonus);
       }
    
       public String toString()// toString()方法,可自动生成
       {
          return super.toString() + "[bonus=" + bonus + "]";
       }
    }
    复制代码

       结果:

         删除程序中Employee类、Manager类中的equals()、hasCode()、toString()方法,背录删除方法

             代码:

            Employee.java

    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;
       }

    @Override
    public boolean equals(Object otherObject) {  //重写equals方法
        // 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() {   //重写hashCode方法
        // TODO Auto-generated method stub
        return Objects.hash(name,salary,hireDay);
    }

    @Override
    public String toString() {  //重写toString方法
        // TODO Auto-generated method stub
        return getClass().getName()+"[name="+name+",salary="+salary+",hireday="+hireDay+"]";
    }
    }

          Manager.java

    package equals;

    public class Manager extends Employee  //Manager类(子类)继承Employee类(父类)
    {
       private double bonus;//私有属性

       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;
       }

    @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+"]";
    }

    }

          EqualsTest.java

    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)
       {
          var alice1 = new Employee("Alice Adams", 75000, 1987, 12, 15);
          var alice2 = alice1;
          var alice3 = new Employee("Alice Adams", 75000, 1987, 12, 15);
          var 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);
    
          var carl = new Manager("Carl Cracker", 80000, 1987, 12, 15);
          var 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());
       }
    }

          结果:

             测试程序2:

         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;

            掌握ArrayList类的定义及用法;

         在程序中相关代码处添加新知识的注释;

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

              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用三个Employee类填充staff数组列表
          var staff = new ArrayList<Employee>();//动态数组,可以灵活设置数组的大小
    
          staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15));//在列表中插入元素,
          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%每个人的薪水提高5%
          for (Employee e : staff)
             e.raiseSalary(5);
    
          // print out information about all Employee objects
          for (Employee e : staff)//for each循环,遍历数组列表
             System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay=" 
                + e.getHireDay());
       }
    }

           Employee.java

    package arrayList;
    
    import java.time.*;
    
    public class Employee
    {
       private String name;//私有属性
       private double salary;//私有属性
       private LocalDate hireDay;//私有属性
    
       public Employee(String name, double salary, int year, int month, int day)//构造器
       {
          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)//访问器
       {
          double raise = salary * byPercent / 100;
          salary += raise;
       }
    }

           结果:

    注:ArrayList :动态数组,可以动态增加和减少元素,灵活设置数组的大小。
                  三个构造器: public ArrayList();默认构造器  public ArrayList(ICollection); 
            public ArrayList(int); 指定大小来初始化内部的数组

             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
          var staff = new ArrayList<Employee>();
    
          staff.add(new Employee("Carl Cracker", 75000, 1987, 12, 15));//在列表中插入元素,
          staff.add(new Employee("Harry Hacker", 50000, 1989, 10, 1));
          staff.add(new Employee("Tony Tester", 40000, 1990, 3, 15));
          System.out.println(staff.get(1));
          staff.set(2, new Employee("DXY", 1000, 1999, 7, 21));
          System.out.println(staff.size());
          staff.remove(0);
    
          // raise everyone's salary by 5%
          for (Employee e : staff)
             e.raiseSalary(5);
    
          // print out information about all Employee objects
          for (Employee e : staff)//for each循环,遍历数组列表
             System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay=" 
                + e.getHireDay());
       }
    }

          注:get()方法获得下标的储存位置

          set()方法修改ArrayList<>并添加new Employee("DXY", 1000, 1999, 7, 21)

        get()方法获得元素输出

        remove()方法删除数组元素

        size()方法得到长度。

        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;

        掌握枚举类的定义及用法;

        在程序中相关代码处添加新知识的注释;

           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。

            5-12:

    package enums;
    
    import java.util.*;
    
    /**
     * This program demonstrates enumerated types.
     * @version 1.0 2004-05-24
     * @author Cay Horstmann
     */
    public class EnumTest//主类
    {  
       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();  //字符串转换为大写
          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//枚举类型,是enum的子类
    {
       SMALL("S"), MEDIUM("M"), LARGE("L"), EXTRA_LARGE("XL");//需传入参数
    
       private Size(String abbreviation) { this.abbreviation = abbreviation; }
       public String getAbbreviation() { return abbreviation; }
    
       private String abbreviation;
    }

          结果:

              删除程序中Size枚举类,背录删除代码

         代码:

    
    
    package equals;
    
    public class Manager extends Employee  //Manager类(子类)继承Employee类(父类)
    {
       private double bonus;//私有属性
    
       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;
       }
    
    @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+"]";
    }
    
    }
    
    
    
     

      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:

    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);  
        }  
    }

           结果:

    注:int... intArray,...是可变参数,是int型,也可以改为其他型的   eg:String...StringArray

         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。

    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 {
    //补全本类定义
    }
    程序运行结果如下:
    Parent's Constructor with a boolean parameter
    Son's Constructor without parameter
    Son's method()
    Parent's method()

          代码:

    public class Demo1 {
          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 {     //补全本类定义
         Son(){
             super(false);
             System.out.println("Son's Constructor without parameter");
         }
         public void method() {
             System.out.println("Son's method()");
             super.method();
         }
     }

         结果:

    3. 实验总结:

      通过本次实验,我学习到了:1.四种访问权限修饰符的使用特点   2.Object类   3.ArrayList类的方法    4.枚举类定义方法及用途

            通过本次实验,加深了我对java继承特点的理解,并在助教讲解后对四种访问权限修饰符有了更深层面的认识,掌握了ArrayList类,枚举类,对java的学习有了更深的了解。通过线上线下学习,及实验课的练习,我对继承这一章的知识有了明确的把握,但在知识掌握上还是不足。在实验中遇到了许多问题,归根结底是知识掌握的不熟,在同学的帮助下基本解决了问题。在课余时间还是要加强对知识的理解,多练习。

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  • 原文地址:https://www.cnblogs.com/budinge/p/11655449.html
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