实验七 继承附加实验
实验时间 2018-10-11
1、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。
2、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(); /*在下面分别调用 demo1 demo2 demo3 demo4 test1 test2 test3 test4方法 和t1 t2 t3 t3 e1 e2 e3 e4属性,好好理解继承和权限修饰符的用法与区别*/ test2.demo1(); test2.demo3(); String e2=test2.e2; System.out.println(e2); } } |
实验2 第五章测试程序反思,继承知识总结。
测试程序1:
Ÿ 编辑、编译、调试运行教材程序5-8、5-9、5-10(教材174页-177页);
Ÿ 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;/*** 这个程序演示了等值方法 * @version 1.12 2012-01-26* @author Cay Horstmann*///实现了Employee类和Manager类的equals、hashCode和toString方法
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;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){// 快速测试,以查看对象是否相同if (this == otherObject) return true;// 如果explicit的参数为null,则必须返回falseif (otherObject == null) return false;//如果类不匹配,它们就不能相等。 if (getClass() != otherObject.getClass()) return false;// 现在我们知道另一个对象是非null的Employee类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+ "]";}
}
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;// Suff.Enter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 + "]";}
}
测试程序2:
Ÿ 编辑、编译、调试运行教材程序5-11(教材182页);
Ÿ 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.*;/*** 这个程序演示了ARAYLIST类.* @version 1.11 2012-01-26* @author Cay Horstmann*/
public class ArrayListTest
{public static void main(String[] args){// 用三名员工对象填写员工数组列表 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);//打印所有员工对象的信息 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:
Ÿ 编辑、编译、调试运行程序5-12(教材189页);
Ÿ 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.*;/*** 这个程序演示枚举类型 .* @version 1.0 2004-05-24* @author Cay Horstmann*/
public class EnumTest
{ // 所有枚举类型都是Enum的子类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);//将size设置成Size.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;
}
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。
实验总结:
这次实验让我在前一次实验的基础上对继承有了进一步的了解,但通过测试发现了很多的问题,我会利用闲暇时间进一步的学习这一章和后面的内容,同时复习前面的章节内容,希望对Java可以有更深一步的了解。