如何使用公历比较没有时间戳的日期？

Question

如何使用公历比较没有时间戳的日期？在下面提供的示例中，两个结果都必须是 true.

package com.tutorialspoint;

import java.util.*;

public class GregorianCalendarDemo {

   public static void main(String[] args) {

   // create a new calendar
   GregorianCalendar cal1 = 
   (GregorianCalendar) GregorianCalendar.getInstance();

   // print the current date and time
   System.out.println("" + cal1.getTime());

   // create a second calendar equal to first one
   GregorianCalendar cal2 = (GregorianCalendar) (Calendar) cal1.clone();

   // print cal2
   System.out.println("" + cal2.getTime());

   // compare the two calendars
   System.out.println("Cal1 and Cal2 are equal:" + cal1.equals(cal2));

   // change cal 2 a bit
   cal2.add(GregorianCalendar.MINUTE, 5);

   // compare the two calendars
   System.out.println("Cal1 and Cal2 are equal:" + cal1.equals(cal2));

   }
}

Answer 1

由于您使用 equals 比较两个实例，只有当它们表示完全相同的时间戳时它们才相等。请参阅 java.util.GregorianCalendar#equals Javadoc：

Compares this GregorianCalendar to the specified Object. The result is true if and only if the argument is a GregorianCalendar object that represents the same time value (millisecond offset from the Epoch) under the same Calendar parameters and Gregorian change date as this object.

因此，将 cal2 的值更改为其他值后，它永远不会等于 cal1。

Answer 2

如果您想比较日期，请使用以下代码：

// compare the two dates
System.out.println("Date1 and date2 are equal:" + cal1.getTime().equals(cal2.getTime()));

Answer 3

假设 cal1 和 cal2 具有相同的时区（即 cal1.getTimeZone().equals(cal2.getTimeZone())），您可以使用以下代码仅比较日期：

cal1.get(Calendar.YEAR) == cal2.get(Calendar.YEAR) &&
cal1.get(Calendar.DAY_OF_YEAR) == cal2.get(Calendar.DAY_OF_YEAR)

如何使用公历比较没有时间戳的日期？

How to compare dates without time stamp using Gregorian Calendar?

java

gregorian-calendar