如何在Java中计算“时间之前”？

getrelativeDateTime 函数将会给你一个类似于 Whatsapp 通知的日期时间。
如果需要获取未来的相对日期时间，可以添加相应的条件。这个函数是专门为了获取类似于 Whatsapp 通知的日期时间而创建的。

private static String getRelativeDateTime(long date) {
    SimpleDateFormat DateFormat = new SimpleDateFormat("MMM dd, yyyy", Locale.getDefault());
    SimpleDateFormat TimeFormat = new SimpleDateFormat(" hh:mm a", Locale.getDefault());
    long now = Calendar.getInstance().getTimeInMillis();
    long startOfDay = StartOfDay(Calendar.getInstance().getTime());
    String Day = "";
    String Time = "";
    long millSecInADay = 86400000;
    long oneHour = millSecInADay / 24;
    long differenceFromNow = now - date;

    if (date > startOfDay) {
        if (differenceFromNow < (oneHour)) {
            int minute = (int) (differenceFromNow / (60000));
            if (minute == 0) {
                int sec = (int) differenceFromNow / 1000;
                if (sec == 0) {
                    Time = "Just Now";
                } else if (sec == 1) {
                    Time = sec + " second ago";
                } else {
                    Time = sec + " seconds ago";
                }
            } else if (minute == 1) {
                Time = minute + " minute ago";
            } else if (minute < 60) {
                Time = minute + " minutes ago";
            }
        } else {
            Day = "Today, ";
        }
    } else if (date > (startOfDay - millSecInADay)) {
        Day = "Yesterday, ";
    } else if (date > (startOfDay - millSecInADay * 7)) {
        int days = (int) (differenceFromNow / millSecInADay);
        Day = days + " Days ago, ";
    } else {
        Day = DateFormat.format(date);
    }
    if (Time.isEmpty()) {
        Time = TimeFormat.format(date);
    }
    return Day + Time;
}

public static long StartOfDay(Date date) {
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(date);
    calendar.set(Calendar.HOUR_OF_DAY, 0);
    calendar.set(Calendar.MINUTE, 0);
    calendar.set(Calendar.SECOND, 0);
    calendar.set(Calendar.MILLISECOND, 0);
    return calendar.getTimeInMillis();
}

为了简单和更新的响应，遵循更近期的Java 8及以上版本

import java.time.*;
import java.time.temporal.*;

public class Time {
    public static void main(String[] args) {

        System.out.println(LocalTime.now().minus(8, ChronoUnit.MINUTES));
        System.out.println(LocalTime.now().minus(8, ChronoUnit.HOURS));
        System.out.println(LocalDateTime.now().minus(8, ChronoUnit.DAYS));
        System.out.println(LocalDateTime.now().minus(8, ChronoUnit.MONTHS));
    }
}

这是使用Java Time API的版本，旨在解决处理日期和时间方面的过去问题。

Javadoc

版本8 https://docs.oracle.com/javase/8/docs/api/index.html?java/time/package-summary.html

版本11 https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/time/package-summary.html

W3Schools教程 - https://www.w3schools.com/java/java_date.asp

DZone文章 - https://dzone.com/articles/java-8-date-and-time

对我来说它有效

public class TimeDifference {
    int years;
    int months;
    int days;
    int hours;
    int minutes;
    int seconds;
    String differenceString;

    public TimeDifference(@NonNull Date curdate, @NonNull Date olddate) {

        float diff = curdate.getTime() - olddate.getTime();
        if (diff >= 0) {
            int yearDiff = Math.round((diff / (AppConstant.aLong * AppConstant.aFloat)) >= 1 ? (diff / (AppConstant.aLong * AppConstant.aFloat)) : 0);
            if (yearDiff > 0) {
                years = yearDiff;
                setDifferenceString(years + (years == 1 ? " year" : " years") + " ago");
            } else {
                int monthDiff = Math.round((diff / AppConstant.aFloat) >= 1 ? (diff / AppConstant.aFloat) : 0);
                if (monthDiff > 0) {
                    if (monthDiff > AppConstant.ELEVEN) {
                        monthDiff = AppConstant.ELEVEN;
                    }
                    months = monthDiff;
                    setDifferenceString(months + (months == 1 ? " month" : " months") + " ago");
                } else {
                    int dayDiff = Math.round((diff / (AppConstant.bFloat)) >= 1 ? (diff / (AppConstant.bFloat)) : 0);
                    if (dayDiff > 0) {
                        days = dayDiff;
                        if (days == AppConstant.THIRTY) {
                            days = AppConstant.TWENTYNINE;
                        }
                        setDifferenceString(days + (days == 1 ? " day" : " days") + " ago");
                    } else {
                        int hourDiff = Math.round((diff / (AppConstant.cFloat)) >= 1 ? (diff / (AppConstant.cFloat)) : 0);
                        if (hourDiff > 0) {
                            hours = hourDiff;
                            setDifferenceString(hours + (hours == 1 ? " hour" : " hours") + " ago");
                        } else {
                            int minuteDiff = Math.round((diff / (AppConstant.dFloat)) >= 1 ? (diff / (AppConstant.dFloat)) : 0);
                            if (minuteDiff > 0) {
                                minutes = minuteDiff;
                                setDifferenceString(minutes + (minutes == 1 ? " minute" : " minutes") + " ago");
                            } else {
                                int secondDiff = Math.round((diff / (AppConstant.eFloat)) >= 1 ? (diff / (AppConstant.eFloat)) : 0);
                                if (secondDiff > 0) {
                                    seconds = secondDiff;
                                } else {
                                    seconds = 1;
                                }
                                setDifferenceString(seconds + (seconds == 1 ? " second" : " seconds") + " ago");
                            }
                        }
                    }

                }
            }

        } else {
            setDifferenceString("Just now");
        }

    }

    public String getDifferenceString() {
        return differenceString;
    }

    public void setDifferenceString(String differenceString) {
        this.differenceString = differenceString;
    }

    public int getYears() {
        return years;
    }

    public void setYears(int years) {
        this.years = years;
    }

    public int getMonths() {
        return months;
    }

    public void setMonths(int months) {
        this.months = months;
    }

    public int getDays() {
        return days;
    }

    public void setDays(int days) {
        this.days = days;
    }

    public int getHours() {
        return hours;
    }

    public void setHours(int hours) {
        this.hours = hours;
    }

    public int getMinutes() {
        return minutes;
    }

    public void setMinutes(int minutes) {
        this.minutes = minutes;
    }

    public int getSeconds() {
        return seconds;
    }

    public void setSeconds(int seconds) {
        this.seconds = seconds;
    } }