Java日历: Subtract two Dates to get difference in days between the two

Question

这个问题已经有答案了:

Calculating the difference between two Java date instances (46 个回答)

已关闭 6 年前。

我想检查我的用户登录以来已经有多少天了:

Calendar lastLogin = Calendar.getInstance();
lastLogin.setTime(randomPlayer.getLastLogin());
Calendar today = Calendar.getInstance();

如何减去这个值以获得两者之间的天数差异？即自上次登录以来的天数。

Answer 1

我建议使用LocalDate相反:

import java.time.LocalDate;
import java.time.temporal.ChronoUnit;

public class DaysBetween {

    public static void main(String[] args) {
        LocalDate lastLogin = LocalDate.of(2017, 4, 1);
        LocalDate today = LocalDate.now();
        System.out.println(daysBetween(lastLogin, today));
    }

    private static long daysBetween(LocalDate from, LocalDate to) {
        return ChronoUnit.DAYS.between(from, to);
    }
}

或者，如果您真的想坚持使用日历:

import java.time.temporal.ChronoUnit;
import java.util.Calendar;

public class DaysBetween {

    public static void main(String[] args) {
        Calendar lastLogin = Calendar.getInstance();
        lastLogin.set(Calendar.YEAR, 2017);
        lastLogin.set(Calendar.MONTH, 3);
        lastLogin.set(Calendar.DAY_OF_MONTH, 1);
        Calendar today = Calendar.getInstance();
        System.out.println(daysBetween(lastLogin, today));
    }

    private static long daysBetween(Calendar from, Calendar to) {
        return ChronoUnit.DAYS.between(from.toInstant(), to.toInstant());
    }
}