理论部分：
第五章：继承
1.继承用已有类来构建新类的一种机制。
2..继承的特点：具有层次结构，子类继承了父类的域和方法。
3.继承的优点：代码可重用性，父类的域和方法可用于子类，可以轻松定义子类，设计应用程序变得更加简单。
4.继承层次：
实验六 继承定义与使用
实验时间 2018-9-28
1、实验目的与要求
(1) 理解继承的定义；
(2) 掌握子类的定义要求
(3) 掌握多态性的概念及用法；
(4) 掌握抽象类的定义及用途；
(5) 掌握类中4个成员访问权限修饰符的用途；
(6) 掌握抽象类的定义方法及用途；
(7)掌握Object类的用途及常用API；
(8) 掌握ArrayList类的定义方法及用法；
(9) 掌握枚举类定义方法及用途。
2、实验内容和步骤
实验1： 导入第5章示例程序，测试并进行代码注释。
测试程序1：
? 在elipse IDE中编辑、调试、运行程序5-1 （教材152页-153页） ；
? 掌握子类的定义及用法；
? 结合程序运行结果，理解并总结OO风格程序构造特点，理解Employee和Manager类的关系子类的用途，并在代码中添加注释。
package inheritance;
/**
* This program demonstrates inheritance.
*
* @version 1.21 2004-02-21
* @author Cay Horstmann
*/
public class ManagerTest {
public static void main(String[] args) {
// construct a Manager object
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);// 执行完该行之后bonus为0
boss.setBonus(5000);//set调用更改器方法将bonus改为5000
Employee[] staff = new Employee[3];//定义一个Employee类，new后使用构造器方法并将该数组初始化为3。
// fill the staff array with Manager and Employee objects
staff[0] = boss;//boss是Employee类的子类对象。
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);
//staff也是Employee类。
// print out information about all Employee objects
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());//使用get调用访问器 方法
}
}
package inheritance;
public class Manager extends Employee
{
private double bonus;
/**
* @param name the employee‘s name
* @param salary the salary
* @param year the hire year
* @param month the hire month
* @param day the hire day
*/
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 b)
{
bonus = b;
}
}
package inheritance;
/**
* This program demonstrates inheritance.
* @version 1.21 2004-02-21
* @author Cay Horstmann
*/
public class ManagerTest
{
public static void main(String[] args)
{
// construct a Manager object
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
boss.setBonus(5000);
Employee[] staff = new Employee[3];
// fill the staff array with Manager and Employee objects
staff[0] = boss;
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);
// print out information about all Employee objects
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
}
}
运行结果：
测试程序2：
? 编辑、编译、调试运行教材PersonTest程序（教材163页-165页)；
? 掌握超类的定义及其使用要求；
? 掌握利用超类扩展子类的要求；
? 在程序中相关代码处添加新知识的注释。
/**
* This program demonstrates abstract classes.
* @version 1.01 2004-02-21
* @author Cay Horstmann
*/
public class PersonTest//主类
{
public static void main(String[] args)
{
Person[] people = new Person[2];
//用Employee类和Student类填充people数组
people[0] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
people[1] = new Student("Maria Morris", "computer science");
//打印出所有person类的名字和其他描述
for (Person p : people)
System.out.println(p.getName() + ", " + p.getDescription());
}
}
public abstract class Person//抽象类：Person
{
public abstract String getDescription();
private String name;//传建一个私有属性
public Person(String name)//构造器
{
this.name = name;
}
public String getName()//访问器
{
return name;
}
}
public class Student extends Person//子类：Student类继承Person类
{
private String major;//创建一个私有属性major
/**
* @param nama the student‘s name
* @param major the student‘s major
*/
public Student(String name, String major)//构造器
{
super(name);//子类直接调用超类中的name属性
this.major = major;
}
public String getDescription()//访问器
{
return "a student majoring in " + major;
}
}
import java.time.*;
public class Employee extends Person//子类：Employee类继承Person类
{
private double salary;
private LocalDate hireDay;
//两个私有属性
public Employee(String name, double salary, int year, int month, int day)//构造器
{
super(name);//子类直接调用超类中的name
this.salary = salary;
hireDay = LocalDate.of(year, month, day);
}
public double getSalary()
{
return salary;
}
public LocalDate getHireDay()
{
return hireDay;
}
public String getDescription()
{
return String.format("an employee with a salary of $%.2f", salary);
}
//访问器
public void raiseSalary(double byPercent)
{
double raise = salary * byPercent / 100;
salary += raise;
}//定义两个局部变量
}
运行结果：
测试程序3：
? 编辑、编译、调试运行教材程序5-8、5-9、5-10，结合程序运行结果理解程序（教材174页-177页）；
? 掌握Object类的定义及用法；
? 在程序中相关代码处添加新知识的注释。
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;
// 检查这个和其他属于同一个类
return bonus == other.bonus;
}
public int hashCode()
{
return java.util.Objects.hash(super.hashCode(), bonus);
}
public String toString()
{
return super.toString() + "[bonus=" + bonus + "]";
}
}
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)
{
// 快速检查对象是否相同
// 这里获得一个对象参数，第一个if语句判断两个引用是否是同一个，如果是那么这两个对象肯定相等
if (this == otherObject) return true;
// 如果显式参数为空，则必须返回false
if (otherObject == null) return false;
if (getClass() != otherObject.getClass()) return false;
// 父类引用子类的对象的出现，然后再判断对象的属性是否相同
Employee other = (Employee) otherObject;
// 测试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
+ "]";
}
}
运行结果：
测试程序4：
? 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。
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)
{
// 用三个Employee对象填充staff数组列表
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));
// 把每个人的薪水提高5%
for (Employee e : staff)
e.raiseSalary(5);
// 打印所有Employee对象的信息
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary() + ",hireDay="
+ e.getHireDay());
}
}
//employee类：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：
测试程序5：
? 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。
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)//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;
实验2：编程练习1
? 定义抽象类Shape：
属性：不可变常量double PI，值为3.14；
方法：public double getPerimeter()；public double getArea())。
? 让Rectangle与Circle继承自Shape类。
? 编写double sumAllArea方法输出形状数组中的面积和和double sumAllPerimeter方法输出形状数组中的周长和。
? main方法中
1）输入整型值n，然后建立n个不同的形状。如果输入rect，则再输入长和宽。如果输入cir，则再输入半径。
2） 然后输出所有的形状的周长之和，面积之和。并将所有的形状信息以样例的格式输出。
3） 最后输出每个形状的类型与父类型，使用类似shape.getClass()(获得类型)，shape.getClass().getSuperclass()(获得父类型);
思考sumAllArea和sumAllPerimeter方法放在哪个类中更合适？
输入样例:
3
rect
1 1
rect
2 2
cir
1
输出样例:
18.28
8.14
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
实验一代码及结果如下：
主类：
package demo1;
import java.util.Scanner;
public class Text1 {
public static void main(String[] args) {
// TODO 自动生成的方法存
@SuppressWarnings("resource")
Scanner in = new Scanner(System.in);
String rect = "rect";
String cir = "cir";
System.out.println("请输入不同的形状个数:");
int n = in.nextInt();
shape[] num = new shape[n];
for (int i = 0; i < n; i++) {
System.out.println("请输入形状类型 (rect or cir):");
String input = in.next();
if (input.equals(rect)) {
System.out.println("长和宽");
double length = in.nextDouble();
double width = in.nextDouble();
System.out.println("Rectangle[" + "length:" + length + " width:" + width + "]");
num[i] = new Rectangle(width, length);
}
if (input.equals(cir)) {
System.out.println("半径 ");
double radius = in.nextDouble();
System.out.println("Circle[" + "radius:" + radius + "]");
num[i] = new Circle(radius);
}
}
Text1 c = new Text1();
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;
}
}
抽象类Shape：
public abstract class shape {
double PI = 3.14;
abstract double getPerimeter();
abstract double getArea();
}
circle类：
public class Circle extends shape {
private double radius;
public Circle(double radius) {
}
public double getPerimeter()
{
double Perimeter=2*PI*radius;
return Perimeter;
}
public double getArea()
{
double Area=PI*radius*radius;
return Area;
}
}
Rectangle类：
public class Rectangle extends shape {
private double length;
private double width;
public Rectangle(double width, double length) {
this.length = length;
this.width = width;
}
public double getPerimeter() {
double Perimeter=2*(length + width);
return Perimeter ;
}
public double getArea() {
double Area= length * width;
return Area;
}
}
运行结果：
实验3： 编程练习2
编制一个程序，将身份证号.txt 中的信息读入到内存中，输入一个身份证号或姓名，查询显示查询对象的姓名、身份证号、年龄、性别和出生地。
程序如下：
package demo2;
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 Demo2 {
private static ArrayList<Student> studentlist;
public static void main(String[] args) {
studentlist = new ArrayList<>();
@SuppressWarnings("resource")
Scanner scanner = new Scanner(System.in);
File file = new File("D:\\身份证号\\身份证号.txt");
try {
FileInputStream fis = new FileInputStream(file);
@SuppressWarnings("resource")
BufferedReader in = new BufferedReader(new InputStreamReader(fis));
String temp = null;
while ((temp = in.readLine()) != null) {
@SuppressWarnings("resource")
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("所找信息文件找不到");
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
System.out.println("所找信息文件读取错误");
e.printStackTrace();
}
boolean isTrue = true;
while (isTrue) {
System.out.println("欢迎来到信息查询系统,请选择你的操作");
System.out.println("1.按姓名查询");
System.out.println("2.按身份证号查询");
System.out.println("3.退出");
int nextInt = scanner.nextInt();
switch (nextInt) {
case 1:
System.out.println("请输入姓名");
String studentname = scanner.next();
int nameint = findStudentByname(studentname);
if (nameint != -1) {
System.out.println("查找信息为：身份证号:" + studentlist.get(nameint).getNumber() + " 姓名:"
+ studentlist.get(nameint).getName() + " 性别:" + studentlist.get(nameint).getSex()
+ " 年龄:" + studentlist.get(nameint).getYear() + " 地址:"
+ studentlist.get(nameint).getProvince());
} else {
System.out.println("不存在该人");
}
break;
case 2:
System.out.println("请输入身份证号");
String studentid = scanner.next();
int idint = findStudentByid(studentid);
if (idint != -1) {
System.out.println("查找信息为：身份证号:" + studentlist.get(idint).getNumber() + " 姓名:"
+ studentlist.get(idint).getName() + " 性别:" + studentlist.get(idint).getSex() + " 年龄:"
+ studentlist.get(idint).getYear() + " 地址:" + studentlist.get(idint).getProvince());
} else {
System.out.println("不存在该人");
}
break;
case 3:
isTrue = false;
System.out.println("程序已退出!");
break;
default:
System.out.println("输入有误");
}
}
}
public static int findStudentByname(String name) {
int flag = -1;
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).getId().equals(id)) {
flag = i;
}
}
return flag;
}
}
封装类如下所示：
public class Student {
private String name;
private String id;
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 getId() {
return id;
}
public void setId(String id) {
this.id = id;
}
public String getNumber() {
// TODO 自动生成的方法存根
return number;
}
public void setNumber(String number) {
this.number = number;
}
public String getSex() {
// TODO 自动生成的方法存根
return sex;
}
public void setSex(String sex) {
// TODO 自动生成的方法存根
this.sex = sex;
}
public String getYear() {
// TODO 自动生成的方法存根
return year;
}
public void setYear(String year) {
// TODO 自动生成的方法存根
this.year = year;
}
public String getProvince() {
// TODO 自动生成的方法存根
return province;
}
public void setProvince(String province) {
// TODO 自动生成的方法存根
this.province = province;
}
}
运行结果如下：
实验总结：通过本次实验二让我更加明确了封装的概念，以及读取文件的操作，通过实验一让我更进一步的理解了继承的概念，在此次代码注释过程中，我发现了自己的不足之处在于，对有些代码还是不太清楚其语义，以及其含义，上次老师讲授代码的含义时，对我帮助极大，希望老师还可以选择讲一些代码的作用。这样在我自己学习时，就可结合老师的讲授去理解。
原文地址：https://www.cnblogs.com/li-xiaojing/p/9725219.html
时间： 2024-07-31 21:05:35