Wednesday, February 1, 2012

3 Example to Compare two Dates in Java

comparing dates in Java is common need for Java programmer, now and then we need to compare two dates to check whether two dates are equals, less than or greater than each other, some time we also needs to check if one dates comes in between two dates. Java provides multiple ways to compare two Dates in Java which is capable of performing Date comparison and letting you know whether two dates are same, one date come before or after another date in Java. In last couple of article we have seen how to convert String to Date in Java and Converting  Date to String in Java and here we will see three different example of comparing two dates in Java.

How to compare two dates in Java 

There are multiple ways to compare two dates in Java and below is 3 ways I used to compare multiple dates in Java
  1) by Using classic CompareTo method of Date class.
  2) by using equals(), before() and after method of Date class.
  3) by using equals(), before() and after method of Calendar class in Java.

example of date compare in javaAll three ways are capable of performing date comparison but my favorite is either using compareTo be in consistent with how we compare two objects in Java or by using Date's equals(), before and after() method because that sounds more natural to me.  Here is code example of comparing different dates in Java.


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

public class HashtableDemo {

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

        DateFormat df = new SimpleDateFormat("dd-MM-yyyy");

        //comparing date using compareTo method in Java
        System.out.println("Comparing two Date in Java using CompareTo method");
        compareDatesByCompareTo(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByCompareTo(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByCompareTo(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

        //comparing dates in java using Date.before, Date.after and Date.equals
        System.out.println("Comparing two Date in Java using Date's before, after and equals method");
        compareDatesByDateMethods(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByDateMethods(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByDateMethods(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

        //comparing dates in java using Calendar.before(), Calendar.after and Calendar.equals()
        System.out.println("Comparing two Date in Java using Calendar's before, after and equals method");
        compareDatesByCalendarMethods(df, df.parse("01-01-2012"), df.parse("01-01-2012"));
        compareDatesByCalendarMethods(df, df.parse("02-03-2012"), df.parse("04-05-2012"));
        compareDatesByCalendarMethods(df, df.parse("02-03-2012"), df.parse("01-02-2012"));

    }

    public static void compareDatesByCompareTo(DateFormat df, Date oldDate, Date newDate) {
        //how to check if date1 is equal to date2
        if (oldDate.compareTo(newDate) == 0) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //checking if date1 is less than date 2
        if (oldDate.compareTo(newDate) < 0) {
            System.out.println(df.format(oldDate) + " is less than " + df.format(newDate));
        }

        //how to check if date1 is greater than date2 in java
        if (oldDate.compareTo(newDate) > 0) {
            System.out.println(df.format(oldDate) + " is greater than " + df.format(newDate));
        }
    }

    public static void compareDatesByDateMethods(DateFormat df, Date oldDate, Date newDate) {
        //how to check if two dates are equals in java
        if (oldDate.equals(newDate)) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //checking if date1 comes before date2
        if (oldDate.before(newDate)) {
            System.out.println(df.format(oldDate) + " comes before " + df.format(newDate));
        }

        //checking if date1 comes after date2
        if (oldDate.after(newDate)) {
            System.out.println(df.format(oldDate) + " comes after " + df.format(newDate));
        }
    }

    public static void compareDatesByCalendarMethods(DateFormat df, Date oldDate, Date newDate) {

        //creating calendar instances for date comparision
        Calendar oldCal = Calendar.getInstance();
        Calendar newCal = Calendar.getInstance();

        oldCal.setTime(oldDate);
        newCal.setTime(newDate);

        //how to check if two dates are equals in java using Calendar
        if (oldCal.equals(newCal)) {
            System.out.println(df.format(oldDate) + " and " + df.format(newDate) + " are equal to each other");
        }

        //how to check if one date comes before another using Calendar
        if (oldCal.before(newCal)) {
            System.out.println(df.format(oldDate) + " comes before " + df.format(newDate));
        }

        //how to check if one date comes after another using Calendar
        if (oldCal.after(newCal)) {
            System.out.println(df.format(oldDate) + " comes after " + df.format(newDate));
        }
    }
}

Output:

Comparing two Date in Java using CompareTo method
01-01-2012 and 01-01-2012 are equal to each other
02-03-2012 is less than 04-05-2012
02-03-2012 is greater than 01-02-2012
Comparing two Date in Java using Date's before, after and equals method
01-01-2012 and 01-01-2012 are equal to each other
02-03-2012 comes before 04-05-2012
02-03-2012 comes after 01-02-2012
Comparing two Date in Java using Calendar's before, after and equals method
01-01-2012 and 01-01-2012 are equal to each other
02-03-2012 comes before 04-05-2012
02-03-2012 comes after 01-02-2012

That’s all on comparing two dates in Java. Dates are very important for writing any enterprise java application and good understanding of Dates and Calendar classes, Date Formating always help.

Here are few more Java tutorials you may like.

2 comments :

Anonymous said...

good examples. I would recommend Joda time API for comparing dates or any date related operation in java.

Javin @ Struts interview questions said...

@Anonymous, yes Joda Time could be good choice as well but it also add another dependency on your project.

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