《面向对象程序设计(java)》第七周学习总结

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();

/*以下设计代码分别调用 demo1 demo2 demo3 demo4 test1 test2 test3 test4方法和t1 t2 t3 t3 e1 e2 e3 e4属性,结合程序运行结果理解继承和权限修饰符的用法与区别*/

}

}

实验代码:

 package test1;

 public class Main {
public static void main(String[] args) {
TEST2 test2=new TEST2();
test2.demo1();
test2.demo3();
test2.demo4();
test2.tese2();
test2.tese3();
test2.tese4();
System.out.println(test2.e2);
System.out.println(test2.e3);
System.out.println(test2.e4);
System.out.println(test2.t2);
System.out.println(test2.t3);
System.out.println(test2.t4);
}
}
 package test1;

 public class TEST1 {
private String t1="这是TEST1的私有属性";
public String t2="这是TEST2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");
}
}
 package test1;

 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");
}
}

实验结果:

《面向对象程序设计(java)》第七周学习总结

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;

实验代码:

 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;

 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
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; // 现在我们知道另一个对象是非空雇员
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
+ "]";
}
}
 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;
// super.equals检查这个和其他属于同一个类
return bonus == other.bonus;
}
//获得散列码,看看是否相同
public int hashCode()
{
return java.util.Objects.hash(super.hashCode(), bonus);
} public String toString()
{
return super.toString() + "[bonus=" + bonus + "]";
}
}

实验结果:

《面向对象程序设计(java)》第七周学习总结

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;

实验代码:

 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)
{
// 用三个雇员对象填充工作人员数组列表
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)); // 把每个人的工资提高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;
}
}

实验结果:

《面向对象程序设计(java)》第七周学习总结

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;

实验代码:

 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
{
//枚举类的所有实例必须放在第一行显示。
SMALL("S"), MEDIUM("M"), LARGE("L"), EXTRA_LARGE("XL"); private Size(String abbreviation) { this.abbreviation = abbreviation; }
public String getAbbreviation() { return abbreviation; } private String abbreviation;
}

实验结果:

《面向对象程序设计(java)》第七周学习总结

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:通过这次四个修饰符与三个类的实验,我掌握了四个修饰符的权限范围,了解了三个特殊类的含义及使用方法。但还是有许多细节上的理解不到位和不足,尤其是枚举类的定义和用法还没有完全理解和掌握,还需要努力实践练习以掌握枚举类的含义并巩固其他所学知识。

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