基于 Object 类及包装类的专项实验

2.1 验证性实验

1、用户类（User）的封装与构造方法实现。调试下面的程序，分析程序的功能和运行结果并添加代码注释。

|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class User {​ private String username;​ private String password;​ private String tel;​ ​ public User() {}​ ​ public User(String username, String password, String tel) {​ this.username = username;​ this.password = password;​ this.tel = tel;​ }​ ​ public String getUsername() {​ return username;​ }​ public void setUsername(String username) {​ this.username = username;​ }​ ​ public String getPassword() {​ return password;​ }​ ​ public void setPassword(String password) {​ this.password = password;​ }​ ​ public String getTel() {​ return tel;​ }​ ​ public void setTel(String tel) {​ this.tel = tel;​ }​ } |

2、在上述 User 类中覆盖 toString 方法，格式为 "username：xxx，password：xxx，tel：xxx"。调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|--------------------------------------------------------------------------------------------------------------------|
| @Override​ public String toString() {​ return "username：" + username + "，password：" + password + "，tel：" + tel;​ } |

3、在上述 User 类中覆盖 equals 方法，只要用户名相同则判定为相同对象。调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| @Override​ public boolean equals(Object obj) {​ if (this == obj) return true;​ if (obj == null || getClass() != obj.getClass()) return false;​ User user = (User) obj;​ return username.equals(user.username);​ } |

4、编写测试类，调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| import java.util.Scanner;​ ​ public class UserTest {​ public static void main(String\[\] args) {​ Scanner scanner = new Scanner(System.in);​ ​ System.out.println("请输入第一个用户信息：");​ System.out.print("用户名：");​ String username1 = scanner.nextLine();​ System.out.print("密码：");​ String password1 = scanner.nextLine();​ System.out.print("电话：");​ String tel1 = scanner.nextLine();​ User user1 = new User(username1, password1, tel1);​ ​ System.out.println("请输入第二个用户信息：");​ System.out.print("用户名：");​ String username2 = scanner.nextLine();​ System.out.print("密码：");​ String password2 = scanner.nextLine();​ System.out.print("电话：");​ String tel2 = scanner.nextLine();​ }​ } |

5、学生类（Student）的封装与包装类应用。调试下面的程序，分析程序的功能和运行结果并添加代码注释。

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class Student { private String name; private Integer age; private Double score; public Student() {} public Student(String name, Integer age, Double score) { this.name = name; this.age = (age != null && age >= 0) ? age : null; this.score = (score != null && score >= 0 && score <= 100) ? score : null; } public String getName() { return name; } public Integer getAge() { return age; } public Double getScore() { return score; } public void setName(String name) { this.name = name; } public void setAge(Integer age) { this.age = (age != null && age >= 0) ? age : null; } public void setScore(Double score) { this.score = (score != null && score >= 0 && score <= 100) ? score : null; } } |

6、在上述Student 类基础上覆盖 toString 方法，"姓名：xxx，年龄：xxx，成绩：xxx" ，其中无效数据（null ）显示为 "未填写"。调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| @Override public String toString() { String ageStr = (age != null) ? age.toString() : "未填写"; String scoreStr = (score != null) ? score.toString() : "未填写"; return "姓名：" + name + "，年龄：" + ageStr + "，成绩：" + scoreStr; } |

7、在 Student 类 set 方法基础上，新增 isAgeValid、isScoreValid 方法。调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public boolean isAgeValid() { return age != null && age >= 0; } public boolean isScoreValid() { return score != null && score >= 0 && score <= 100; } |

8、编写测试类，调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class StudentTest { public static void main(String\[\] args) { Scanner scanner = new Scanner(System.in); System.out.println("请输入学生信息："); System.out.print("姓名："); String name = scanner.nextLine(); System.out.print("年龄："); Integer age = null; try { age = Integer.valueOf(scanner.nextLine()); } catch (NumberFormatException e) { // 输入非数字，age保持null } System.out.print("成绩："); Double score = null; try { score = Double.valueOf(scanner.nextLine()); } catch (NumberFormatException e) { // 输入非数字，score保持null } Student student = new Student(name, age, score); System.out.println("学生信息：" + student); System.out.println("年龄是否有效：" + student.isAgeValid()); System.out.println("成绩是否有效：" + student.isScoreValid()); scanner.close(); } } |

9、包装类常用方法综合应用。调试下面的程序，并分析程序的功能和运行结果并添加代码注释。

|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| public class WrapperMethodTest { public static void main(String\[\] args) { String strInt = "100"; int num = Integer.parseInt(strInt); System.out.println("字符串\"100\"转int：" + num); String strDouble = "95.5"; Double d = Double.valueOf(strDouble); System.out.println("字符串\"95.5\"转Double：" + d); System.out.println("int最大值：" + Integer.MAX_VALUE); System.out.println("int最小值：" + Integer.MIN_VALUE); System.out.println("double最大值：" + Double.MAX_VALUE); System.out.println("double最小值：" + Double.MIN_VALUE); Integer a = 50; Integer b = 100; System.out.println("a compareTo b：" + a.compareTo(b)); } } |

2.2 自主设计性实验

10、编程实现学生对象信息输出和比较。

要求：定义 Student 类，属性包括学号（id）、姓名（name）、年龄（age），进行封装并提供 get/set 方法及构造方法；重写 toString 方法，格式为 "id：xxx，name：xxx，age：xxx"；重写 equals 方法，学号相同则为相同对象。编写测试类，创建两个 Student 对象，输入信息并判断是否相同，打印对象信息。​

11、编程实现商品类（Goods）的比较​

要求：定义 Goods 类，属性有商品编号（goodsId）、商品名称（goodsName）、价格（price），完成封装、构造方法；重写 equals 方法，商品编号相同则为相同商品；重写 toString 方法展示商品信息。编写测试类，输入两个商品信息，判断是否为同一商品并打印结果。​