?

? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ????實驗六?繼承定義與使用

實驗目的與要求：

在軟件開發中，通過繼承機制，可以利用已有的數據類型來定義新的數據類型。所定義的新的數據類型不僅擁有新定義的成員，而且還同時擁有舊的成員。因此，類的繼承性使所建立的軟件具有開放性開放性、可擴充性，這是信息組織與分類的行之有效的方法，通過類的繼承關系，使公共的特性能夠共享，簡化了對象、類的創建工作量，增加了代碼的可重用性。運行時多態性是面向對象程序設計代碼重用的一個最強大機制，Java多態性的概念也可以被說成“一個接口，多個方法”。Java實現運行時多態性的基礎是動態方法調度，它是一種在運行時而不是在編譯期調用重載方法的機制。方法的重寫Overriding和重載Overloading是Java多態性的不同表現。重寫Overriding是父類與子類之間多態性的一種表現，重載Overloading是一個類中多態性的一種表現。如果在子類中定義某方法與其父類有相同的名稱和參數，我們說該方法被重寫(Overriding)。子類的對象使用這個方法時，將調用子類中的定義，對它而言，父類中的定義如同被“屏蔽”了。如果在一個類中定義了多個同名的方法，它們或有不同的參數個數或有不同的參數類型，則稱為方法的重載(Overloading)。Overloaded的方法是可以改變返回值的類型。方法的重寫Overriding和重載Overloading是Java多態性的不同表現。當超類對象引用變量引用子類對象時，被引用對象的類型而不是引用變量的類型決定了調用誰的成員方法，但是這個被調用的方法必須是在超類中定義過的，也就是說被子類覆蓋的方法。 （但是如果強制把超類轉換成子類的話，就可以調用子類中新添加而超類沒有的方法了。

二、(1)?理解繼承的定義；(2)?掌握子類的定義要求(3)?掌握多態性的概念及用法；(4)?掌握抽象類的定義及用途；(5)?掌握類中4個成員訪問權限修飾符的用途；(6)?掌握抽象類的定義方法及用途；(7)掌握Object類的用途及常用API；(8)?掌握ArrayList類的定義方法及用法；(9)?掌握枚舉類定義方法及用途。

2、實驗內容和步驟

實驗1：?導入第5章示例程序，測試并進行代碼注釋。

測試程序1：在elipse?IDE中編輯、調試、運行程序5-1?（教材152頁-153頁）?；掌握子類的定義及用法；結合程序運行結果，理解并總結OO風格程序構造特點，理解Employee和Manager類的關系子類的用途，并在代碼中添加注釋。

測試實驗結果如下：

?

?

?

插入此程序的代碼并對其進行注釋，進行更深一步的理解

ManaManager

?

?

Emloyee:

?

?

?

?

?

子類的定義：在有繼承關系的類中extends前面的類則是子類。

超類和子類都是Java程序員常用的兩個類。

測試程序2：

? ? 編輯、編譯、調試運行教材PersonTest程序（教材163頁-165頁)；

? ?掌握超類的定義及其使用要求；

? ?掌握利用超類擴展子類的要求；

? 在程序中相關代碼處添加新知識的注釋。

? 超類：如果在程序中沒有明確的之處超類，Object就是被認為是這個類的超類，如：Public class Employee extebds Object.在java中，每個類都是Object類擴展而來的。當然也可以使用Object類型的變量引用任何類型的對象。

超類擴展子類的要求

代碼的注釋：

?

?

?

?

?

測試程序3：

? ? 編輯、編譯、調試運行教材程序5-8、5-9、5-10，結合程序運行結果理解程序（教材174頁-177頁）；

? ? 掌握Object類的定義及用法；

? ? 在程序中相關代碼處添加新知識的注釋。

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;

???}

?

???public boolean equals(Object otherObject)

???{

??????// 看看這些對象是否相同

??????if (this == otherObject) return true;

?

??????// 如果顯式參數為空，則必須返回false

??????if (otherObject == null) return false;

?

??????// 如果類不匹配，它們就不能相等

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

?

??????// 現在我們知道otherObject是一個非空雇員

??????Employee other = (Employee) otherObject;

?

??????// 測試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()

???{

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

???}

?

???public String toString()

???{

??????return getClass().getName() + "[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay

????????????+ "]";

???}

}

Manager.java:

package equals;

?

public class Manager extends Employee//子類Manager繼承父類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檢查這個和其他屬于同一個類

??????return bonus == other.bonus;

???}

?

???public int hashCode()

???{

??????return java.util.Objects.hash(super.hashCode(), bonus);

???}

?

???public String toString()

???{

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

???}

}

Equals.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)

???{

??????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;

?

/**

?* 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());

???}

}

測試程序4：

? ? ?在elipse IDE中調試運行程序5-11（教材182頁），結合程序運行結果理解程序；

? ? ?掌握ArrayList類的定義及用法；

? ? ?在程序中相關代碼處添加新知識的注釋。

插入程序相關代碼

ArrayList.java:

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)

???{

??????// 用三個Employee對象填充staff數組列表

??????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));

?

??????// 把每個人的薪水提高5%

??????for (Employee e : staff)

?????????e.raiseSalary(5);

?

??????// 打印所有Employee對象的信息

??????for (Employee e : staff)

?????????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;

???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;

???}

}

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;

???}

}

程序測試結果如下：

?

?

測試程序5：

? ? 編輯、編譯、調試運行程序5-12（教材189頁），結合運行結果理解程序；

? ?掌握枚舉類的定義及用法；

? ?在程序中相關代碼處添加新知識的注釋。

插入實例程序的代碼：

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;

}

測試結果如下：

?

?

實驗2：編程練習1

? ??定義抽象類Shape：

? 屬性：不可變常量double PI，值為3.14；

? 方法：public double getPerimeter()；public double getArea())。

??讓Rectangle與Circle繼承自Shape類。

? ??編寫double sumAllArea方法輸出形狀數組中的面積和和double sumAllPerimeter方法輸出形狀數組中的周長和。

? main方法中

1）輸入整型值n，然后建立n個不同的形狀。如果輸入rect，則再輸入長和寬。如果輸入cir，則再輸入半徑。
2）?然后輸出所有的形狀的周長之和，面積之和。并將所有的形狀信息以樣例的格式輸出。
3）?最后輸出每個形狀的類型與父類型，使用類似shape.getClass()(獲得類型)，shape.getClass().getSuperclass()(獲得父類型);

思考sumAllArea和sumAllPerimeter方法放在哪個類中更合適？

輸入樣例:

3

rect

1 1

rect

2 2

cir

1

輸出樣例:

18.28

8.14

[Rectangle [width=1, length=1], Rectangle [width=2, length=2], Circle [radius=1]]

class Rectangle,class Shape

class Rectangle,class Shape

class Circle,class Shape

?程序相關代碼：

shape:

package shape;

import java.util.Scanner;

public class Test {

?public static void main(String[] args) {

??Scanner in = new Scanner(System.in);

??System.out.println("個數");

??int a = in.nextInt();

??System.out.println("種類");

??String rect="rect";

????????String cir="cir";

??Shape[] num=new Shape[a];

??for(int i=0;i<a;i++){

???String input=in.next();

???if(input.equals(rect)) {

???System.out.println("長和寬");

???int length = in.nextInt();

???int width = in.nextInt();

?????????num[i]=new Rectangle(width,length);

?????????System.out.println("Rectangle["+"length:"+length+" ?width:"+width+"]");

?????????}

???if(input.equals(cir)) {

?????????System.out.println("半徑");

??????int radius = in.nextInt();

??????num[i]=new Circle(radius);

??????System.out.println("Circle["+"radius:"+radius+"]");

?????????}

?????????}

?????????Test c=new Test();

?????????System.out.println("求和");

?????????System.out.println(c.sumAllPerimeter(num));

?????????System.out.println(c.sumAllArea(num));

?????????

?????????for(Shape s:num) {

?????????????System.out.println(s.getClass()+","+s.getClass().getSuperclass());

?????????????}

?????????}

?

???????????public double sumAllArea(Shape score[])

???????????{

???????????double sum=0;

???????????for(int i=0;i<score.length;i++)

???????????????sum+= score[i].getArea();

???????????????return sum;

???????????}

???????????public double sumAllPerimeter(Shape score[])

???????????{

???????????double sum=0;

???????????for(int i=0;i<score.length;i++)

???????????????sum+= score[i].getPerimeter();

???????????????return sum;

???????????} ???

}

Test:

package shape;

import java.util.Scanner;

public class Test {

?public static void main(String[] args) {

??Scanner in = new Scanner(System.in);

??System.out.println("個數");

??int a = in.nextInt();

??System.out.println("種類");

??String rect="rect";

????????String cir="cir";

??Shape[] num=new Shape[a];

??for(int i=0;i<a;i++){

???String input=in.next();

???if(input.equals(rect)) {

???System.out.println("長和寬");

???int length = in.nextInt();

???int width = in.nextInt();

?????????num[i]=new Rectangle(width,length);

?????????System.out.println("Rectangle["+"length:"+length+" ?width:"+width+"]");

?????????}

???if(input.equals(cir)) {

?????????System.out.println("半徑");

??????int radius = in.nextInt();

??????num[i]=new Circle(radius);

??????System.out.println("Circle["+"radius:"+radius+"]");

?????????}

?????????}

?????????Test c=new Test();

?????????System.out.println("求和");

?????????System.out.println(c.sumAllPerimeter(num));

?????????System.out.println(c.sumAllArea(num));

?????????

?????????for(Shape s:num) {

?????????????System.out.println(s.getClass()+","+s.getClass().getSuperclass());

?????????????}

?????????}

?

???????????public double sumAllArea(Shape score[])

???????????{

???????????double sum=0;

???????????for(int i=0;i<score.length;i++)

???????????????sum+= score[i].getArea();

???????????????return sum;

???????????}

???????????public double sumAllPerimeter(Shape score[])

???????????{

???????????double sum=0;

???????????for(int i=0;i<score.length;i++)

???????????????sum+= score[i].getPerimeter();

???????????????return sum;

???????????} ???

}

實驗結果如下所示：

?

?

實驗3：?編程練習2

編制一個程序，將身份證號.txt?中的信息讀入到內存中，輸入一個身份證號或姓名，查詢顯示查詢對象的姓名、身份證號、年齡、性別和出生地。

?插入程序代碼：

Main :

?

?本周學習package id1;

?

import java.io.BufferedReader;

import java.io.File;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStreamReader;

import java.util.ArrayList;

import java.util.Scanner;

?

public class Main{

????private static ArrayList<Student> studentlist;

????public static void main(String[] args) {

????????studentlist = new ArrayList<>();

????????Scanner scanner = new Scanner(System.in);

????????File file = new File("D:/身份證號.txt");

????????try {

????????????FileInputStream fis = new FileInputStream(file);

????????????BufferedReader in = new BufferedReader(new InputStreamReader(fis));

????????????String temp = null;

????????????while ((temp = in.readLine()) != null) {

????????????????

????????????????Scanner linescanner = new Scanner(temp);

????????????????

????????????????linescanner.useDelimiter(" "); ???

????????????????String name = linescanner.next();

????????????????String number = linescanner.next();

????????????????String sex = linescanner.next();

????????????????String year = linescanner.next();

????????????????String province =linescanner.nextLine();

????????????????Student student = new Student();

????????????????student.setName(name);

????????????????student.setnumber(number);

????????????????student.setsex(sex);

????????????????student.setyear(year);

????????????????student.setprovince(province);

????????????????studentlist.add(student);

?

????????????}

????????} catch (FileNotFoundException e) {

????????????System.out.println("學生信息文件找不到");

????????????e.printStackTrace();

????????} catch (IOException e) {

????????????System.out.println("學生信息文件讀取錯誤");

????????????e.printStackTrace();

????????}

????????boolean isTrue = true;

????????while (isTrue) {

?

????????????System.out.println("1.按姓名查詢");

????????????System.out.println("2.按身份證號查詢");

????????????System.out.println("3.退出");

????????????int nextInt = scanner.nextInt();

????????????switch (nextInt) {

????????????case 1:

????????????????System.out.println("請輸入姓名");

????????????????String studentname = scanner.next();

????????????????int nameint = findStudentByname(studentname);

????????????????if (nameint != -1) {

????????????????????System.out.println("查找信息為：身份證號:"

????????????????????????????+ studentlist.get(nameint).getnumber() + " ???姓名:"

????????????????????????????+ studentlist.get(nameint).getName() +" ???性別:"

????????????????????????????+studentlist.get(nameint).getsex() ??+" ???年齡:"

????????????????????????????+studentlist.get(nameint).getyaer()+" ?地址:"

????????????????????????????+studentlist.get(nameint).getprovince()

????????????????????????????);

????????????????} else {

????????????????????System.out.println("不存在該學生");

????????????????}

????????????????break;

????????????case 2:

????????????????System.out.println("請輸入身份證號");

????????????????String studentid = scanner.next();

????????????????int idint = findStudentByid(studentid);

????????????????if (idint != -1) {

????????????????????System.out.println("查找信息為：身份證號:"

????????????????????????????+ studentlist.get(idint ).getnumber() + " ???姓名:"

????????????????????????????+ studentlist.get(idint ).getName() +" ???性別:"

????????????????????????????+studentlist.get(idint ).getsex() ??+" ???年齡:"

????????????????????????????+studentlist.get(idint ).getyaer()+" ??地址:"

????????????????????????????+studentlist.get(idint ).getprovince()

????????????????????????????);

????????????????} else {

????????????????????System.out.println("不存在該學生");

????????????????}

????????????????break;

????????????case 3:

????????????????isTrue = false;

????????????????System.out.println("程序已退出!");

????????????????break;

????????????default:

????????????????System.out.println("輸入有誤");

????????????}

????????}

????}

?

????public static int findStudentByname(String name) {

????????int flag = -1;

????????int a[];

????????for (int i = 0; i < studentlist.size(); i++) {

????????????if (studentlist.get(i).getName().equals(name)) {

????????????????flag= i;

????????????}

????????}

????????return flag;

????}

?

????public static int findStudentByid(String id) {

????????int flag = -1;

?

????????for (int i = 0; i < studentlist.size(); i++) {

????????????if (studentlist.get(i).getnumber().equals(id)) {

????????????????flag = i;

????????????}

????????}

????????return flag;

????} ??

Student:

?

?

?

public class Student {

?

????private String name;

????private String number ;

????private String sex ;

????private String year;

????private String province;

???

????public String getName() {

????????return name;

????}

????public void setName(String name) {

????????this.name = name;

????}

????public String getnumber() {

????????return number;

????}

????public void setnumber(String number) {

????????this.number = number;

????}

????public String getsex() {

????????return sex ;

????}

????public void setsex(String sex ) {

????????this.sex =sex ;

????}

????public String getyaer() {

????????return year;

????}

????public void setyear(String year ) {

????????this.year=year ;

????}

????public String getprovince() {

????????return province;

????}

????public void setprovince(String province) {

????????this.province=province ;

????}

}

實驗結果如下所示：

?

?實驗總結：

通過這一周的學習以及自己在后期的自學過程當中，我深入了解了什么叫做繼承，以及在繼承中所包含的類型有哪些。繼承是用已有類來構建新類的一種機制，當定義了一個新類繼承了一個類時，這個新類繼承一個類時，這個新類就繼承了這個類的方法和域。而且繼承是具有層次的，其代碼也是可重用的，可以輕松定義子類。首先在學習過程當中我們學習了類，超類和子類的定義，讓我明白了父類和子類時相對的。還學習了泛型數組列表與對象包裝器與自動裝箱，在后面還介紹了反射的概念，它是在程序運行期間發現更多的類及其屬性的能力。并體會頗多，在今后的日子里我會好好深入學習java知識。

?

?

轉載于:https://www.cnblogs.com/xuezhiqian/p/9750573.html

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