如何通过实例化获取 localdate 的年龄

Question

我如何使用实例化集获取 localdate 的年龄，我尝试使用 localdate 和设置的年龄，但它不起作用。我试过将年龄作为 LocalDate 而不是 Int，但它也不起作用，我是一个新程序员，我希望你们能帮我解决 this.Its 编译错误

  package main;
    import Usuarios.User;
    import java.time.LocalDate;
    /**
     *
     * @author Gustavo
     */
    public class Main {
        
        public static void main(String[] args) {
    
    
            User person1 = new User();
            person1.setName("Mike");
            person1.setbirthdateUser(LocalDate.of(1970, 5, 17));
            person1.setAge(LocalDate.now().getYear() - birthdateUser.getYear());
    
            /*person1.age = LocalDate.now().getYear() - person1.birthdateUser.getYear();*/
    
            System.out.println(person1.getName() + " has " +  person1.getAge() + " years old");

Answer 1

这一行编译错误：

person1.setAge(LocalDate.now().getYear() - birthdateUser.getYear());

是因为birthdateUser.getYear()没有使用Person对象person1来调用方法。应该是

person1.setAge(LocalDate.now().getYear() - person1.getBirthdateUser().getYear());

也就是说，在我看来，没有必要在对象上设置 age。最好传递出生日期，让对象根据这条数据计算年龄。因此，我对此（使用 Java 记录）的解决方案如下：

public class Main {
    public static void main(String[] args) {
        String name = "Mike";
        LocalDate birthdate = LocalDate.of(1970, 5, 17);
        User person1 = new User(name, birthdate);
        System.out.println(person1.name() + ", born in " + person1.birthdate + ", is " +  person1.age() + " years old");
    }
    
    private static record User (String name, LocalDate birthdate) {
        
        public long age() {
            return ChronoUnit.YEARS.between(birthdate, LocalDate.now());
        }
    }
}

这输出：

Mike, born in 1970-05-17, is 51 years old

请注意，即使我使用的是记录，我仍然可以创建一个自定义方法，该方法 returns 根据传递给被调用对象的出生日期计算年龄。这实际上非常酷，因为即使年龄发生变化，因为我没有存储它，它也不会违反对象“不可变”的约束，因为年龄不是记录中的字段。它是一个计算值。这使得这个对象本质上是线程安全的（不完全）。

更新：一个稍微好一点的版本，有更多实用方法。

public class Main {
    public static void main(String[] args) {
        String name = "Mike";
        LocalDate birthdate = LocalDate.of(1970, 5, 17);
        User person1 = new User(name, birthdate);
        System.out.println(person1.toString());
        System.out.println(person1.name() + " was born on a " + person1.getDayBornOn());
    }
    
    private static record User (String name, LocalDate birthdate) {
        
        public long age() {
            return ChronoUnit.YEARS.between(birthdate, LocalDate.now());
        }
        
        public int getBirthYear() {
            return birthdate.getYear();
        }
        
        public String getBirthdateMonth() {
            return capitalizeFirstLetter(birthdate.getMonth().toString());
        }
        
        public String getBirthday() {
            return getBirthdateMonth() + " " + birthdate.getDayOfMonth();
        }
        
        public String getDateOfBirth() {
            return getBirthday() + ", " + getBirthYear();
        }
        
        public String getDayBornOn() {
            
            return capitalizeFirstLetter(birthdate.getDayOfWeek().name());
        }
        
        private String capitalizeFirstLetter(String string) {
            string = string.toLowerCase();
            String upperLetter = String.valueOf(string.charAt(0)).toUpperCase();
            return upperLetter + string.substring(1);
        }
        
        @Override
        public String toString() {
            return this.name() + ", born in " + this.getDateOfBirth() + ", is " +  this.age() + " years old";
        }
    }
}

现在输出：

Mike, born in May 17, 1970, is 51 years old
Mike was born on a Sunday

Answer 2

这个有效：

    public static void main(String[] args) {
            
    LocalDate birthDate = LocalDate.of(1970, 5, 17);
    LocalDate currentDate = LocalDate.now();
    int age = Period.between(birthDate, currentDate).getYears();

    System.out.println("Age is: " + age);
   }

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