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。
测试实验结果如下：
插入此程序的代码并对其进行注释，进行更深一步的理解
ManagerTest
package inheritance;
/
public class ManagerTest
{
public static void main(String[] args)
{
// 构建管理者对象
Manager boss = new Manager("Carl Cracker", 80000, 1987, 12, 15);
boss.setBonus(5000);
Employee[] staff = new Employee[3];//定义一个包含3个雇员的数组
// 用管理者和员工对象填充员工数组
staff[0] = boss;
staff[1] = new Employee("Harry Hacker", 50000, 1989, 10, 1);
staff[2] = new Employee("Tommy Tester", 40000, 1990, 3, 15);
// 打印关于所有员工对象的信息
for (Employee e : staff)
System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());
//输出每个人的薪水
}
}
Manager
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; } }
Emloyee:
package inheritance; 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 inheritance; 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; } }
子类的定义：在有继承关系的类中extends前面的类则是子类。
超类和子类都是Java程序员常用的两个类。
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。
超类：如果在程序中没有明确的之处超类，Object就是被认为是这个类的超类，如：Public class Employee extebds Object.在java中，每个类都是Object类扩展而来的。当然也可以使用Object类型的变量引用任何类型的对象。
超类扩展子类的要求
代码的注释：
package abstractClasses; import java.time.*; public class Employee extends Person { private double salary; private LocalDate hireDay; public Employee(String name, double salary, int year, int month, int day) { super(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); } public void raiseSalary(double byPercent) { double raise = salary * byPercent / 100; salary += raise; } }
package abstractClasses; /** * This program demonstrates abstract classes. * @version 1.01 2004-02-21 * @author Cay Horstmann */ public class PersonTest { public static void main(String[] args) { Person[] people = new Person[2]; // 用Student和Employee对象填充人员数组 people[0] = new Employee("Harry Hacker", 50000, 1989, 10, 1); people[1] = new Student("Maria Morris", "computer science"); // 打印所有person对象的名称和描述 for (Person p : people) System.out.println(p.getName() + ", " + p.getDescription()); } }
package abstractClasses; public class Student extends Person { private String major; /** * @param nama the student's name * @param major the student's major */ public Student(String name, String major) { // 将n传递给父类函数 super(name); this.major = major; } public String getDescription() { return "a student majoring in " + major; } }
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。
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) { // 看看这些对象是否相同 if (this == otherObject) return true; // 如果显式参数为空，则必须返回false if (otherObject == null) return false; // 如果类不匹配，它们就不能相等 if (getClass() != otherObject.getClass()) return false; // 现在我们知道otherObject是一个非空雇员 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 + "]"; } }
Manager.java:
package equals; public class Manager extends Employee//子类Manager继承父类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 + "]"; } }
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()); } }
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。
插入程序相关代码
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.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; } }
程序测试结果如下：
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。
插入实例程序的代码：
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); 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; }
测试结果如下：
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
[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
程序相关代码：
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("个数"); int a = in.nextInt(); System.out.println("种类"); 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("长和宽"); int length = in.nextInt(); int width = in.nextInt(); num[i]=new Rectangle(width,length); System.out.println("Rectangle["+"length:"+length+" "+width+"]"); } if(input.equals(cir)) { System.out.println("半径"); 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("个数"); int a = in.nextInt(); System.out.println("种类"); 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("长和宽"); int length = in.nextInt(); int width = in.nextInt(); num[i]=new Rectangle(width,length); System.out.println("Rectangle["+"length:"+length+" "+width+"]"); } if(input.equals(cir)) { System.out.println("半径"); 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; } }
实验结果如下所示：
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。
插入程序代码：
Main :
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:/身份证号.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("学生信息文件找不到"); e.printStackTrace(); } catch (IOException e) { System.out.println("学生信息文件读取错误"); e.printStackTrace(); } boolean isTrue = true; while (isTrue) { 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).getyaer()+" 地址:" +studentlist.get(nameint).getprovince() ); } else { System.out.println("不存在该学生"); } 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 ).getyaer()+" 地址:" +studentlist.get(idint ).getprovince() ); } else { System.out.println("不存在该学生"); } 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; 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:
package id1; 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 ; } }
实验结果如下所示：
本周学习总结：
通过将近一周的学习以及自己在后期的自学过程当中，我深入了解了什么叫做继承，以及在继承中所包含的类型有哪些。继承是用已有类来构建新类的一种机制，当定义了一个新类继承了一个类时，这个新类继承一个类时，这个新类就继承了这个类的方法和域。而且继承是具有层次的，其代码也是可重用的，可以轻松定义子类。首先在学习过程当中我们学习了类，超类和子类的定义，让我明白了父类和子类时相对的。还学习了泛型数组列表与对象包装器与自动装箱，在后面还介绍了反射的概念，它是在程序运行期间发现更多的类及其属性的能力。