How to compare two string dates in Java?

Question

I have two dates in String format like below -

String startDate = "2014/09/12 00:00";

String endDate = "2014/09/13 00:00";

I want to make sure startDate should be less than endDate. startDate should not be greater than endDate.

How can I compare these two dates and return boolean accordingly?

Solution 1

Convert them to an actual Date object, then call before.

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd h:m");
System.out.println(sdf.parse(startDate).before(sdf.parse(endDate)));

Recall that parse will throw a ParseException, so you should either catch it in this code block, or declare it to be thrown as part of your method signature.

Solution 2

Here is a fully working demo. For date formatting, refer - http://docs.oracle.com/javase/6/docs/api/java/text/SimpleDateFormat.html

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

public class Dating {

    public static void main(String[] args) {

        String startDate = "2014/09/12 00:00";
        String endDate = "2014/09/13 00:00";

        try {
            Date start = new SimpleDateFormat("yyyy/MM/dd HH:mm", Locale.ENGLISH)
                    .parse(startDate);
            Date end = new SimpleDateFormat("yyyy/MM/dd HH:mm", Locale.ENGLISH)
                    .parse(endDate);

            System.out.println(start);
            System.out.println(end);

            if (start.compareTo(end) > 0) {
                System.out.println("start is after end");
            } else if (start.compareTo(end) < 0) {
                System.out.println("start is before end");
            } else if (start.compareTo(end) == 0) {
                System.out.println("start is equal to end");
            } else {
                System.out.println("Something weird happened...");
            }

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

    }

}

Solution 3

tl;dr

Use modern java.time classes to parse the inputs into LocalDateTime objects by defining a formatting pattern with DateTimeFormatter, and comparing by calling isBefore.

java.time

The modern approach uses the java.time classes.

Define a formatting pattern to match your inputs.

Parse as LocalDateTime objects, as your inputs lack an indicator of time zone or offset-from-UTC.

String startInput = "2014/09/12 00:00";
String stopInput = "2014/09/13 00:00";

DateTimeFormatter f = DateTimeFormatter.ofPattern( "uuuu/MM/dd HH:mm" );

LocalDateTime start = LocalDateTime.parse( startInput , f ) ;
LocalDateTime stop = LocalDateTime.parse( stopInput , f ) ;
boolean isBefore = start.isBefore( stop ) ;

Dump to console.

System.out.println( start + " is before " + stop + " = " + isBefore );

See this code run live at IdeOne.com.

2014-09-12T00:00 is before 2014-09-13T00:00 = true

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

• 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 6 and Java SE 7
  • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android bundle implementations of the java.time classes.
  • For earlier Android (<26), the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

The ThreeTen-Extra project 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.

Solution 4

Use SimpleDateFormat to convert to Date to compare:

SimpleDateFormat sdf = new SimpleDateFormat("yyyy/MM/dd HH:mm");
Date start = sdf.parse(startDate);
Date end = sdf.parse(endDate);
System.out.println(start.before(end));

Solution 5

The simplest and safest way would probably be to parse both of these strings as dates, and compare them. You can convert to a date using a SimpleDateFormat, use the before or after method on the date object to compare them.

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