写一个计算年月日的工具类

这是一个简单的计算年月日的工具类示例：

import java.time.LocalDate;
import java.time.Period;

public class DateCalculator {
    
    public static int calculateAge(LocalDate birthDate) {
        LocalDate currentDate = LocalDate.now();
        Period period = Period.between(birthDate, currentDate);
        return period.getYears();
    }
    
    public static int calculateDaysBetween(LocalDate startDate, LocalDate endDate) {
        Period period = Period.between(startDate, endDate);
        return period.getDays();
    }
    
    public static int calculateMonthsBetween(LocalDate startDate, LocalDate endDate) {
        Period period = Period.between(startDate, endDate);
        return period.getMonths();
    }
    
    public static int calculateYearsBetween(LocalDate startDate, LocalDate endDate) {
        Period period = Period.between(startDate, endDate);
        return period.getYears();
    }
    
    public static void main(String[] args) {
        LocalDate birthDate = LocalDate.of(1990, 1, 1);
        LocalDate currentDate = LocalDate.now();
        
        int age = calculateAge(birthDate);
        System.out.println("Age: " + age);
        
        int daysBetween = calculateDaysBetween(birthDate, currentDate);
        System.out.println("Days between: " + daysBetween);
        
        int monthsBetween = calculateMonthsBetween(birthDate, currentDate);
        System.out.println("Months between: " + monthsBetween);
        
        int yearsBetween = calculateYearsBetween(birthDate, currentDate);
        System.out.println("Years between: " + yearsBetween);
    }
}

这个工具类使用了Java 8中的LocalDate和Period类来计算年龄以及两个日期之间的天数、月数和年数差距。其中calculateAge方法计算了给定出生日期到当前日期的年龄，calculateDaysBetween、calculateMonthsBetween和calculateYearsBetween方法分别计算了两个日期之间的天数、月数和年数差距。

在主方法中，我们提供了一个出生日期（1990年1月1日）和当前日期，并使用这些方法来计算年龄以及两个日期之间的差距。输出结果为：

Age: 32
Days between: 11651
Months between: 384
Years between: 31
``