How to compare dates in Java

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How to compare dates in Java
By mkyong | January 18, 2010 | Updated : November 15, 2016 | Viewed : 930,987 | +4,252 pv/w
Few examples show you how to compare two dates in Java. Updated with Java 8 examples.

1. Date.compareTo()
A classic method to compare two java.util.Date in Java.

Return value is 0 if both dates are equal.
Return value is greater than 0 , if Date is after the date argument.
Return value is less than 0, if Date is before the date argument.
TestDate.java

package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class TestDate {

public static void main(String[] args) throws ParseException {

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date1 = sdf.parse("2009-12-31");
Date date2 = sdf.parse("2010-01-31");

System.out.println("date1 : " + sdf.format(date1));
System.out.println("date2 : " + sdf.format(date2));

if (date1.compareTo(date2) > 0) {
System.out.println("Date1 is after Date2");
} else if (date1.compareTo(date2) < 0) {
System.out.println("Date1 is before Date2");
} else if (date1.compareTo(date2) == 0) {
System.out.println("Date1 is equal to Date2");
} else {
System.out.println("How to get here?");
}

}

}
Output

date1 : 2009-12-31
date2 : 2010-01-31
Date1 is before Date2

2. Date.before(), Date.after() and Date.equals()
A more user friendly method to compare two java.util.Date

TestDate2.java

package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;

public class TestDate2 {

public static void main(String[] args) throws ParseException {

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date1 = sdf.parse("2009-12-31");
Date date2 = sdf.parse("2010-01-31");

System.out.println("date1 : " + sdf.format(date1));
System.out.println("date2 : " + sdf.format(date2));

if (date1.after(date2)) {
System.out.println("Date1 is after Date2");
}

if (date1.before(date2)) {
System.out.println("Date1 is before Date2");
}

if (date1.equals(date2)) {
System.out.println("Date1 is equal Date2");
}

}

}
Output

date1 : 2009-12-31
date2 : 2010-01-31
Date1 is before Date2

3. Calender.before(), Calender.after() and Calender.equals()
Example to compare two java.util.Calendar

TestDate3.java

package com.mkyong.date;

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

public class TestDate3 {

public static void main(String[] args) throws ParseException {

SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
Date date1 = sdf.parse("2009-12-31");
Date date2 = sdf.parse("2010-01-31");

System.out.println("date1 : " + sdf.format(date1));
System.out.println("date2 : " + sdf.format(date2));

Calendar cal1 = Calendar.getInstance();
Calendar cal2 = Calendar.getInstance();
cal1.setTime(date1);
cal2.setTime(date2);

if (cal1.after(cal2)) {
System.out.println("Date1 is after Date2");
}

if (cal1.before(cal2)) {
System.out.println("Date1 is before Date2");
}

if (cal1.equals(cal2)) {
System.out.println("Date1 is equal Date2");
}
}

}
Output

date1 : 2009-12-31
date2 : 2010-01-31
Date1 is before Date2
4. Java 8
In Java 8, you can use the new isBefore(), isAfter(), isEqual() and compareTo() to compare LocalDate, LocalTime and LocalDateTime.

Review the following example to compare two java.time.LocalDate

TestDate4.java

package com.mkyong.date;

import java.time.LocalDate;
import java.time.format.DateTimeFormatter;

public class TestDate4 {

public static void main(String[] args) {

DateTimeFormatter sdf = DateTimeFormatter.ofPattern("yyyy-MM-dd");
LocalDate date1 = LocalDate.of(2009, 12, 31);
LocalDate date2 = LocalDate.of(2010, 01, 31);

System.out.println("date1 : " + sdf.format(date1));
System.out.println("date2 : " + sdf.format(date2));

System.out.println("Is...");
if (date1.isAfter(date2)) {
System.out.println("Date1 is after Date2");
}

if (date1.isBefore(date2)) {
System.out.println("Date1 is before Date2");
}

if (date1.isEqual(date2)) {
System.out.println("Date1 is equal Date2");
}

System.out.println("CompareTo...");
if (date1.compareTo(date2) > 0) {

System.out.println("Date1 is after Date2");

} else if (date1.compareTo(date2) < 0) {

System.out.println("Date1 is before Date2");

} else if (date1.compareTo(date2) == 0) {

System.out.println("Date1 is equal to Date2");

} else {

System.out.println("How to get here?");

}
}

}
Output

date1 : 2009-12-31
date2 : 2010-01-31
Is...
Date1 is before Date2
CompareTo...
Date1 is before Date2

http://www.mkyong.com/java/how-to-compare-dates-in-java/
http://www.mkyong.com/tutorials/java-date-time-tutorials/

How to compare dates in Java

标签：EDA   com   friend   oca   output   pareto   examples   datetime   classic   

原文地址：https://www.cnblogs.com/shy1766IT/p/10105196.html