Java 将字符串日期与今天的日期进行比较
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Comparing string date with today's date
提问by sok
So I have a string which is "2014-06-30 15:27" and if it is today's date it should only return "15:27" else "30/06/2014". I've already tried simpleDateFormat.parse but it didn't work very well.
所以我有一个字符串是“2014-06-30 15:27”，如果是今天的日期，它应该只返回“15:27”，否则返回“30/06/2014”。我已经尝试过 simpleDateFormat.parse 但效果不佳。
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采纳答案by fipple
final String stringDate = "2014-07-17 23:59";
SimpleDateFormat inputFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm");
Date date = inputFormat.parse(stringDate);
Calendar calendarDate = Calendar.getInstance();
calendarDate.setTime(date);
Calendar midnight = Calendar.getInstance();
midnight.set(Calendar.HOUR_OF_DAY, 0);
midnight.set(Calendar.MINUTE, 0);
midnight.set(Calendar.SECOND, 0);
midnight.set(Calendar.MILLISECOND, 0);
if (calendarDate.compareTo(midnight) >= 0)
{
SimpleDateFormat timeFormat = new SimpleDateFormat("HH:mm");
System.out.println(timeFormat.format(date));
}
else
{
SimpleDateFormat dateTimeForm = new SimpleDateFormat("dd/MM/yyyy HH:mm");
System.out.println(dateTimeForm.format(date));
}
回答by Basil Bourque
LocalDateTime
LocalDateTime
First parse the string as a LocalDateTime. Replace the SPACE in the middle with Tto comply with standard ISO 8601 format. The java.time classes support ISO 8601 formats by default.
首先将字符串解析为LocalDateTime. 将中间的 SPACE 替换T为符合标准 ISO 8601 格式。java.time 类默认支持 ISO 8601 格式。
LocalDateTime ldt = LocalDateTime.parse ( "2014-06-30 15:27".replace ( " " , "T" ) );
ldt.toString(): 2014-06-30T15:27
ldt.toString(): 2014-06-30T15:27
Such a value has no real meaning. The input string lacked any clue about offset-from-UTC or time zone. So we do not know if this is 3 PM in Auckland NZ or 3 PM in Québec Canada, two very different moments. You should to assign the offset or time zone indicated by your business situation. Search Stack Overflow for how to do this, focussing on classes OffsetDateTimeand ZonedDateTime. I'll skip over this crucial issue for now.
这样的值没有实际意义。输入字符串缺乏关于 UTC 偏移量或时区的任何线索。所以我们不知道这是新西兰奥克兰的下午 3 点还是加拿大魁北克的下午 3 点，这是两个截然不同的时刻。您应该根据您的业务情况指定偏移量或时区。搜索 Stack Overflow 以了解如何执行此操作，重点关注类OffsetDateTime和ZonedDateTime. 现在我将跳过这个关键问题。
LocalDate
LocalDate
Extract a date-only value. The LocalDateclass represents a date-only value without time-of-day and without time zone.
提取仅限日期的值。该LocalDate级表示没有时间一天和不同时区的日期，唯一的价值。
LocalDate ld = ldt.toLocalDate();
Today
今天
A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris Franceis a new day while still “yesterday” in Montréal Québec.
时区对于确定日期至关重要。对于任何给定时刻，日期因地区而异。例如，在法国巴黎午夜过后几分钟是新的一天，而在魁北克蒙特利尔仍然是“昨天” 。
ZoneId z = ZoneId.of( "America/Montreal" );
LocalDate today = LocalDate.now( z );
Comparison
比较
You can compare LocalDateobjects by calling methods such as compareTo, equals, isEqual, isBefore, isAfter.
您可以LocalDate通过调用诸如compareTo、equals、isEqual、isBefore、 之类的方法来比较对象isAfter。
if( today.isEqual( ld ) ) {
return ldt.toLocalTime();
} else {
return ld;
}
About java.time
关于java.time
The java.timeframework is built into Java 8 and later. These classes supplant the troublesome old legacydate-time classes such as java.util.Date, Calendar, & SimpleDateFormat.
该java.time框架是建立在Java 8和更高版本。这些类取代了麻烦的旧的遗留日期时间类，例如java.util.Date, Calendar, & SimpleDateFormat。
The Joda-Timeproject, now in maintenance mode, advises migration to the java.timeclasses.
现在处于维护模式的Joda-Time项目建议迁移到java.time类。
To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.
要了解更多信息，请参阅Oracle 教程。并在 Stack Overflow 上搜索许多示例和解释。规范是JSR 310。
You may exchange java.timeobjects directly with your database. Use a JDBC drivercompliant with JDBC 4.2or later. No need for strings, no need for java.sql.*classes.
您可以直接与您的数据库交换java.time对象。使用符合JDBC 4.2或更高版本的JDBC 驱动程序。不需要字符串，不需要类。java.sql.*
Where to obtain the java.time classes?
从哪里获得 java.time 类？
- Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
- Java 9 adds some minor features and fixes.
- Java SE 6and Java SE 7
- Most of the java.timefunctionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
- Android
- Later versions of Android bundle implementations of the java.timeclasses.
- For earlier Android (<26), the ThreeTenABPproject adapts ThreeTen-Backport(mentioned above). See How to use ThreeTenABP….
- Java SE 8、Java SE 9、Java SE 10、Java SE 11及更高版本 - 标准 Java API 的一部分，具有捆绑实现。
- Java 9 添加了一些小功能和修复。
- Java SE 6和Java SE 7
- 大部分java.time功能在ThreeTen-Backport中向后移植到 Java 6 & 7 。
- 安卓
- java.time类的更高版本的 Android 捆绑实现。
- 对于早期的 Android（<26），ThreeTenABP项目采用了ThreeTen-Backport（上面提到过）。请参阅如何使用ThreeTenABP ...。
The ThreeTen-Extraproject extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.
该ThreeTen-额外项目与其他类扩展java.time。该项目是未来可能添加到 java.time 的试验场。你可能在这里找到一些有用的类，比如Interval，YearWeek，YearQuarter，和更多。
回答by Howard J
Simply use the Date class...
只需使用 Date 类...
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
Date exitdate = df.parse("2019-01-17");
Date currdate = new Date();
long diff = currdate.getTime() - exitdate.getTime();
long days = TimeUnit.DAYS.convert(diff, TimeUnit.MILLISECONDS);
if(days==0)
{
System.out.println("IS TRUE"+currdate.toString());
return true;
}
