在 Java 静态方法中用“今天”和“昨天”字符串简化日期对象的替换

Simplify replacement of date object with "today" and "yesterday" strings in Java static method

提问by Mat B.

I have following method that I would like to make shorter or faster if nothing else. Please all comments are welcome:

我有以下方法，如果没有别的，我想缩短或加快速度。欢迎大家提出意见：

Bellow method takes a date object, formates it ("EEE hh:mma MMM d, yyyy") and then figures out if the date is today or yesterday and than, if it is, it returns "(Yesterday | Today) hh:mma" formated string.

Bellow 方法接受一个日期对象，对其进行格式化（“EEE hh:mma MMM d, yyyy”），然后确定日期是今天还是昨天，如果是，则返回“（昨天 | 今天）hh:mma " 格式化的字符串。

    public static String formatToYesterdayOrToday(String date) {
    SimpleDateFormat sdf = new SimpleDateFormat("EEE hh:mma MMM d, yyyy");
    Date in = null;

    try {
        in = sdf.parse(date);
    } catch (ParseException e) {
        log.debug("Date parsing error:", e);
    }

    Calendar x = Calendar.getInstance();
    x.setTime(in);

    String hour = Integer.toString(x.get(Calendar.HOUR));
    String minute = Integer.toString(x.get(Calendar.MINUTE));
    String pm_am = x.get(Calendar.AM_PM) == Calendar.AM ? "AM" : "PM";

    x.set(Calendar.HOUR, 0);
    x.set(Calendar.HOUR_OF_DAY, 0);
    x.set(Calendar.MINUTE, 0);
    x.set(Calendar.SECOND, 0);
    x.set(Calendar.MILLISECOND, 0);

    Calendar today = Calendar.getInstance();
    today.set(Calendar.HOUR, 0);
    today.set(Calendar.HOUR_OF_DAY, 0);
    today.set(Calendar.MINUTE, 0);
    today.set(Calendar.SECOND, 0);
    today.set(Calendar.MILLISECOND, 0);

    Calendar yesterday = Calendar.getInstance();
    yesterday.set(Calendar.HOUR, 0);
    yesterday.set(Calendar.HOUR_OF_DAY, 0);
    yesterday.set(Calendar.MINUTE, 0);
    yesterday.set(Calendar.SECOND, 0);
    yesterday.set(Calendar.MILLISECOND, 0);
    yesterday.add(Calendar.DATE, -1);

    if (x.compareTo(today) == 0) {
        return "Today " + hour + ":" + minute + pm_am;
    }
    if (x.compareTo(yesterday) == 0) {
        return "Yesterday " + hour + ":" + minute + pm_am;
    }
    return date;
}

回答by BalusC

Here's how you could improve it with the standard API:

以下是使用标准 API 改进它的方法：

public static String formatToYesterdayOrToday(String date) throws ParseException {
    Date dateTime = new SimpleDateFormat("EEE hh:mma MMM d, yyyy").parse(date);
    Calendar calendar = Calendar.getInstance();
    calendar.setTime(dateTime);
    Calendar today = Calendar.getInstance();
    Calendar yesterday = Calendar.getInstance();
    yesterday.add(Calendar.DATE, -1);
    DateFormat timeFormatter = new SimpleDateFormat("hh:mma");

    if (calendar.get(Calendar.YEAR) == today.get(Calendar.YEAR) && calendar.get(Calendar.DAY_OF_YEAR) == today.get(Calendar.DAY_OF_YEAR)) {
        return "Today " + timeFormatter.format(dateTime);
    } else if (calendar.get(Calendar.YEAR) == yesterday.get(Calendar.YEAR) && calendar.get(Calendar.DAY_OF_YEAR) == yesterday.get(Calendar.DAY_OF_YEAR)) {
        return "Yesterday " + timeFormatter.format(dateTime);
    } else {
        return date;
    }
}

Here's how you could do it with Jodatime:

以下是您如何使用Jodatime做到这一点：

public static String formatToYesterdayOrToday(String date) {
    DateTime dateTime = DateTimeFormat.forPattern("EEE hh:mma MMM d, yyyy").parseDateTime(date);
    DateTime today = new DateTime();
    DateTime yesterday = today.minusDays(1);
    DateTimeFormatter timeFormatter = DateTimeFormat.forPattern("hh:mma");

    if (dateTime.toLocalDate().equals(today.toLocalDate())) {
        return "Today " + timeFormatter.print(dateTime);
    } else if (dateTime.toLocalDate().equals(yesterday.toLocalDate())) {
        return "Yesterday " + timeFormatter.print(dateTime);
    } else {
        return date;
    }
}

回答by tmr

my understanding of the question is provide a simple method to produce output like the following:

我对这个问题的理解是提供一种简单的方法来产生如下输出：

Today at 20:00
Today at 20:30
Today at 21:00
Tomorrow at 06:45
Tomorrow at 07:00
Tomorrow at 08:15

the code below worked for me, but i am new to android and maybe others could point out if the code is not robust. in code below 'timeLong' is the time of my events in epoch time (milliseconds).

下面的代码对我有用，但我是 android 的新手，也许其他人可以指出代码是否健壮。在'timeLong'下面的代码中是我的事件在纪元时间（毫秒）中的时间。

public String convertFromEpochTime (long timeLong) {
    long timeNow = System.currentTimeMillis();

    // get day in relative time
    CharSequence timeDayRelative;
    timeDayRelative = DateUtils.getRelativeTimeSpanString(timeLong, timeNow, DateUtils.DAY_IN_MILLIS, DateUtils.FORMAT_ABBREV_RELATIVE);

    // get hour in 24 hour time
    Format hourFormatter = new SimpleDateFormat("HH:mm");
    String timeHour = hourFormatter.format(timeLong);

    // Log.d(DEBUG_TAG, "time of event: " + timeDayRelative + " at " + timeHour);

    String timeDayHour = timeDayRelative + " at "+ timeHour;

    return timeDayHour;
}

回答by JOG

You wrote "all comments welcome" so here's my way using joda-time. :)

你写了“欢迎所有评论”，所以这是我使用 joda-time 的方式。:)

I am a fan of displaying dates and times in the short and smart way of iPhone's recent calls (similar to google wave posts). That is "hh:mm"if today, "yesterday" or name of weekdayif <7 days, else yyyy-MM-dd.

我喜欢以 iPhone 最近通话的简短而智能的方式显示日期和时间（类似于 google wave 帖子）。如果今天，则为“hh:mm”，如果 <7 天，则为“yesterday”或工作日名称，否则为yyyy-MM-dd。

private static boolean isToday (DateTime dateTime) {
   DateMidnight today = new DateMidnight();
   return today.equals(dateTime.toDateMidnight());
}

private static boolean isYesterday (DateTime dateTime) {
   DateMidnight yesterday = (new DateMidnight()).minusDays(1);
   return yesterday.equals(dateTime.toDateMidnight());
}

private static String getDayString(Date date) {
    String s;

    if (isToday(new DateTime(date)))
        s = "Today";
    else if (isYesterday(new DateTime(date)))
        s = "Yesterday";
    else
        s = weekdayFormat.format(date);

    return s;
}

public static String getDateString_shortAndSmart(Date date) {
    String s;

    DateTime nowDT = new DateTime();
    DateTime dateDT = new DateTime(date);
    int days = Days.daysBetween(dateDT, nowDT).getDays();

    if (isToday(new DateTime(date)))
        s = getHourMinuteString(date);
    else if (days < 7)
        s = getDayString(date);
    else
        s = getDateString(date);

    return s;
}

where I use a set of SimpleDateFormat (as weekdayFormat above) to format the time to the desired strings, and where DateTime and DateMidnight are joda-time classes.

我使用一组 SimpleDateFormat（如上面的 weekdayFormat）将时间格式化为所需的字符串，其中 DateTime 和 DateMidnight 是 joda-time 类。

In these cases the number of elapsed days between two DateTime:s is less relevant than how people would define the time talking about it. Instead of counting days (or milliseconds as I've seen some people do) DateMidnight comes handy here, though other methods would work just as well. :)

在这些情况下，两个 DateTime:s 之间经过的天数与人们如何定义谈论它的时间无关。DateMidnight 在这里派上用场，而不是计算天数（或我见过的一些人所做的毫秒数），尽管其他方法也同样有效。:)

回答by Fabio Guerra

this for today,yesterday,tomorrow

今天，昨天，明天

String formatDate(String fecha){

    String Rfecha=new String();
     SimpleDateFormat formatter = new SimpleDateFormat("dd-MM-yyyy");
     //SimpleDateFormat formatter2 = new SimpleDateFormat("EEEE d MMM");
     SimpleDateFormat formatter2 = new SimpleDateFormat("E, d MMM ");
        try {
           Date hoy=new Date();

            Date date = formatter.parse(fecha);


            String pref="";
           Log.d("hoy long", ""+(hoy.getTime()/ (1000*60*60*24)));
           Log.d("date long", ""+ (date.getTime()/ (1000*60*60*24)));

           int ihoy=(int) (hoy.getTime()/ (1000*60*60*24));
           int idate=(int) (date.getTime()/ (1000*60*60*24));
           int dif=idate-ihoy;



           if(dif==0)
               pref="Today";
           if(dif==1)
               pref="Tomorrow";
           if(dif==-1)
               pref="Yesterday";

            Rfecha=pref+" "+formatter2.format(date);


        } catch (Exception e) {
            e.printStackTrace();
        }

    return Rfecha;
}

回答by George

Another way of comparing dates apart from the accepted answer above using java.util.Date.getTime() (note: long should be used instead of int):

除了上面接受的答案之外，另一种使用 java.util.Date.getTime() 比较日期的方法（注意：应该使用 long 而不是 int）：

Date today=new Date();
Date dateObj=null;
long diff=0;
try{
    dateObj= formater1.parse(date);
    diff=(today.getTime()-dateObj.getTime())/(86400000);
}catch(Exception e){}
String days="TODAY";
if(diff==1){
    days = "YESTERDAY";
}else if(diff>1){
    days = String.valueOf(diff) + " " +"DAYS AGO";
}

<%=days%> would return:

<%=days%> 将返回：

TODAY

YESTERDAY

x DAYS AGO

今天

昨天

x 天前

回答by Basil Bourque

Time Zone

时区

The Question and the other Answers ignore the crucial issue of time zone. That input string lacks any time zone or offset-from-UTC. So that string will be parsed while assuming it represents a date-time in your JVM's current default time zone. Risky business as (a) that assumption may be false, and (b) that default can change at any moment, even duringruntime.

问题和其他答案忽略了时区的关键问题。该输入字符串缺少任何时区或offset-from-UTC。因此该字符串将被解析，同时假设它代表 JVM 当前默认时区中的日期时间。有风险的业务，因为 (a) 假设可能是错误的，以及 (b) 该默认值可以随时更改，即使在运行时也是如此。

Locale

语言环境

The Question and other Answers ignore another crucial issue: Locale. The Locale determines the human language used to translate the name of day and name of month from the input string during parsing (and generating).

问题和其他答案忽略了另一个关键问题：Locale. Locale 确定用于在解析（和生成）期间从输入字符串翻译日期名称和月份名称的人类语言。

If not specified the JVM's current default Locale will be used for translation. Just as with time zone, your JVM's default Locale can change at any moment, even duringruntime.

如果未指定，将使用 JVM 当前的默认语言环境进行翻译。就像时区一样，您的 JVM 的默认区域设置可以随时更改，即使在运行时也是如此。

Better to specify your desired/expected Locale.

最好指定您想要/期望的语言环境。

java.time

时间

The Question and the other Answers use the old date-time classes that have proven to be poorly designed and troublesome. Java 8 and later has the java.timeframework built-in whose classes supplant the old ones.

问题和其他答案使用旧的日期时间类，这些类已被证明设计不良且麻烦。Java 8 及更高版本内置了java.time框架，其类取代了旧框架。

You method to parse a string while generating a new string should be broken up into two methods. One method should parse to obtain date-time objects. The second should take date-time objects and generate the desired string output. Then each can be used separately. And this approach leads us away from thinking of strings as date-time values. Strings are textual representations of date-time values. Your business logic should focus on manipulating those date-time values as objects, not focus on strings.

您在生成新字符串时解析字符串的方法应分解为两种方法。一种方法应该解析以获得日期时间对象。第二个应该采用日期时间对象并生成所需的字符串输出。然后每个都可以单独使用。这种方法使我们不再将字符串视为日期时间值。字符串是日期时间值的文本表示。您的业​​务逻辑应该专注于将这些日期时间值作为对象进行操作，而不是专注于字符串。

Parsing

解析

private ZonedDateTime parseLengthyString ( String input , ZoneId zoneId , Locale locale ) {
    // FIXME: Check for nulls.

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern ( "EEE hh:mma MMM d, uuuu" );
    formatter = formatter.withZone ( zoneId );
    formatter = formatter.withLocale ( locale );
    ZonedDateTime zdt = null;
    try {
        zdt = ZonedDateTime.parse ( input , formatter );
    } catch ( DateTimeParseException e ) {
        // FIXME: handle exeption.
        System.out.println ( "ERROR - e: " + e );
    }
    return zdt; // FIXME: Check for null.
}

Generating

生成

Given a ZonedDateTimein hand from the method above, we can generate a textual representation of its date-time value using a specified Locale for translation of name-of-day and name-of-month.

根据ZonedDateTime上述方法，我们可以使用指定的语言环境生成日期时间值的文本表示，以翻译日名和月名。

To determine if the date-time is for today or yesterday, we only care about the date portion without time of day. For that we can use the LocalDateclass in java.time.

为了确定日期时间是今天还是昨天，我们只关心日期部分而不关心一天中的时间。为此，我们可以使用LocalDatejava.time 中的类。

private String generateLengthyString ( ZonedDateTime zdt , Locale locale ) {
    // FIXME: Check for nulls.

    // Compare the date-only value of incoming date-time to date-only of today and yesterday.
    LocalDate localDateIncoming = zdt.toLocalDate ();

    Instant instant = Instant.now ();
    ZonedDateTime now = ZonedDateTime.now ( zdt.getZone () ); // Get current date-time in same zone as incoming ZonedDateTime.
    LocalDate localDateToday = now.toLocalDate ();
    LocalDate localDateYesterday = localDateToday.minusDays ( 1 );

    DateTimeFormatter formatter = null;
    if ( localDateIncoming.isEqual ( localDateToday ) ) {
        formatter = DateTimeFormatter.ofPattern ( "'Today' hh:mma" , locale ); // FIXME: Localize "Today".
    } else if ( localDateIncoming.isEqual ( localDateYesterday ) ) {
        formatter = DateTimeFormatter.ofPattern ( "'Yesterday' hh:mma" , locale ); // FIXME: Localize "Yesterday".
    } else {
        formatter = DateTimeFormatter.ofPattern ( "EEE hh:mma MMM d, uuuu" , locale );
    }

    String output = zdt.format ( formatter );
    return output; // FIXME: Check for null.
}

Example

例子

Exercise those two methods.

练习这两种方法。

Arbitrarily choosing a time zone of America/New_Yorkas the Question does not specify.

America/New_York随意选择时区问题未指定。

String input = "Sat 11:23AM Feb 6, 2016";
ZoneId zoneId = ZoneId.of ( "America/New_York" );
Locale locale = Locale.US;
ZonedDateTime zdt = this.parseLengthyString ( input , zoneId , locale );

String output = this.generateLengthyString ( zdt , locale );

By the way, you can ask java.time to automatically format the output string according to the cultural norms of the Locale instead of hard-coding a format.

顺便说一句，您可以要求 java.time 根据 Locale 的文化规范自动格式化输出字符串，而不是对格式进行硬编码。

String outputPerLocale = zdt.format ( DateTimeFormatter.ofLocalizedDateTime ( FormatStyle.MEDIUM ) );

Dump to console.

转储到控制台。

System.out.println ( "input: " + input + " | zdt: " + zdt + " | Instant: " + zdt.toInstant () + " | output: " | output + " + outputPerLocale: " + outputPerLocale );

input: Sat 11:23AM Feb 6, 2016 | zdt: 2016-02-06T11:23-05:00[America/New_York] | Instant: 2016-02-06T16:23:00Z | output: Today 11:23AM | outputPerLocale: Feb 6, 2016 11:23:00 AM

输入：2016 年 2 月 6 日星期六上午 11:23 | zdt: 2016-02-06T11:23-05:00[美国/纽约] | 即时：2016-02-06T16:23:00Z | 输出：今天上午 11:23 | outputPerLocale：2016 年 2 月 6 日上午 11:23:00

By the way, I suggest putting a SPACE before the AMor PMfor easier reading.

顺便说一句，我建议在AM或之前放置一个空格PM以便于阅读。

回答by Uberto

Look at jodatime: http://joda-time.sourceforge.net/

看jodatime：http://joda-time.sourceforge.net/

this is some example code from the doc:

这是文档中的一些示例代码：

public boolean isAfterPayDay(DateTime datetime) {
  if (datetime.getMonthOfYear() == 2) {   // February is month 2!!
    return datetime.getDayOfMonth() > 26;
  }
  return datetime.getDayOfMonth() > 28;
}

public Days daysToNewYear(LocalDate fromDate) {
  LocalDate newYear = fromDate.plusYears(1).withDayOfYear(1);
  return Days.daysBetween(fromDate, newYear);
}

public boolean isRentalOverdue(DateTime datetimeRented) {
  Period rentalPeriod = new Period().withDays(2).withHours(12);
  return datetimeRented.plus(rentalPeriod).isBeforeNow();
}

public String getBirthMonthText(LocalDate dateOfBirth) {
  return dateOfBirth.monthOfYear().getAsText(Locale.ENGLISH);
}

回答by Kishan Solanki

I know I am late to this party. But I have shortest solution for this problem. If you want to show "Today" or "Yesterday" based on the Datethen you just need to use this

我知道我参加这个聚会迟到了。但我对这个问题有最短的解决方案。如果你想根据日期显示“今天”或“昨天”，那么你只需要使用这个

String strDate = "";
if (DateUtils.isToday(date.getTime()))
    strDate = "Today";
else if (DateUtils.isToday(date.getTime() + DateUtils.DAY_IN_MILLIS))
    strDate = "Yesterday";

here variable date is the Dateobject.

这里变量 date 是Date对象。

回答by NarendraSoni

This is extended versino of Balusc's implementation.

这是Balusc 实现的扩展版本。

Try this, i implemented it using joda-datatime2.2.jar and SimpleDateFormat

试试这个，我使用 joda-datatime2.2.jar 和 SimpleDateFormat 实现它

import java.text.SimpleDateFormat;
import java.util.Date;
import org.joda.time.DateMidnight;
import org.joda.time.DateTime;
import org.joda.time.Days;
public class SmartDateTimeUtil {
private static String getHourMinuteString(Date date){
    SimpleDateFormat hourMinuteFormat = new SimpleDateFormat(" h:m a");
    return hourMinuteFormat.format(date);
}

private static String getDateString(Date date){
    SimpleDateFormat dateStringFormat = new SimpleDateFormat("EEE',' MMM d y',' h:m a");
    return dateStringFormat.format(date);
}

private static boolean isToday (DateTime dateTime) {
       DateMidnight today = new DateMidnight();
       return today.equals(dateTime.toDateMidnight());
}

private static boolean isYesterday (DateTime dateTime) {
       DateMidnight yesterday = (new DateMidnight()).minusDays(1);
       return yesterday.equals(dateTime.toDateMidnight());
}

private static boolean isTomorrow(DateTime dateTime){
    DateMidnight tomorrow = (new DateMidnight()).plusDays(1);
       return tomorrow.equals(dateTime.toDateMidnight());
}
private static String getDayString(Date date) {
        SimpleDateFormat weekdayFormat = new SimpleDateFormat("EEE',' h:m a");
        String s;
        if (isToday(new DateTime(date)))
            s = "Today";
        else if (isYesterday(new DateTime(date)))
            s = "Yesterday," + getHourMinuteString(date);
        else if(isTomorrow(new DateTime(date)))
            s = "Tomorrow," +getHourMinuteString(date);
        else
            s = weekdayFormat.format(date);
        return s;
}

public static String getDateString_shortAndSmart(Date date) {
        String s;
        DateTime nowDT = new DateTime();
        DateTime dateDT = new DateTime(date);
        int days = Days.daysBetween(dateDT, nowDT).getDays();   
        if (isToday(new DateTime(date)))
            s = "Today,"+getHourMinuteString(date);
        else if (days < 7)
            s = getDayString(date);
        else
            s = getDateString(date);
        return s;
}

}

Simple cases to use and test the Util class:

使用和测试 Util 类的简单案例：

import java.util.Calendar;
import java.util.Date;

public class SmartDateTimeUtilTest {
    public static void main(String[] args) {
        System.out.println("Date now:"+SmartDateTimeUtil.getDateString_shortAndSmart(new Date()));
        System.out.println("Date 5 days before :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(-5)));
        System.out.println("Date 1 day before :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(-1)));
        System.out.println("Date last month:"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureMonth(-1)));
        System.out.println("Date last year:"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDate(-1)));
        System.out.println("Date 1 day after :"+SmartDateTimeUtil.getDateString_shortAndSmart(getFutureDay(1)));
    }
    public static Date getFutureDate(int numberOfYears){
        Calendar c = Calendar.getInstance();
        c.setTime(new Date());
        c.add(Calendar.YEAR, numberOfYears); 
        return c.getTime();
    }
    public static Date getFutureMonth(int numberOfYears){
        Calendar c = Calendar.getInstance();
        c.setTime(new Date());
        c.add(Calendar.MONTH, numberOfYears); 
        return c.getTime();
    }

    public static Date getFutureDay(int numberOfYears){
        Calendar c = Calendar.getInstance();
        c.setTime(new Date());
        c.add(Calendar.DATE, numberOfYears); 
        return c.getTime();
    }
}