Date compareTo() method in Java with examples

The compareTo() method of Java Date class compares two dates and sort them for order.

Syntax:

public int compareTo(Date anotherDate)

Parameters: The function accepts a single parameter anotherDate which specifies the date to be compared .

Return Value: The function gives three return values specified below:

• It returns the value 0 if the argument Date is equal to this Date.
• It returns a value less than 0 if this Date is before the Date argument.
• It returns a value greater than 0 if this Date is after the Date argument.

Exception: The function throws a single exception that is NullPointerException if anotherDate is null.

Program below demonstrates the above mentioned function:

// Java code to demonstrate
// compareTo() function of Date class

import java.util.Date;
import java.util.Calendar;
public class GfG {
    // main method
    public static void main(String[] args)
    {

        // creating a Calendar object
        Calendar c = Calendar.getInstance();

        // set Month
        // MONTH starts with 0 i.e. ( 0 - Jan)
        c.set(Calendar.MONTH, 11);

        // set Date
        c.set(Calendar.DATE, 05);

        // set Year
        c.set(Calendar.YEAR, 1996);

        // creating a date object with specified time.
        Date dateOne = c.getTime();

        System.out.println("Date 1: "
                           + dateOne);

        // creating a date of object
        // storing the current date
        Date currentDate = new Date();

        System.out.println("Date 2: "
                           + currentDate);

        // compares
        System.out.println("On Comparison: "
                           + currentDate
                                 .compareTo(dateOne));
    }
}

Output:

Date 1: Thu Dec 05 08:17:55 UTC 1996
Date 2: Wed Jan 02 08:17:55 UTC 2019
On Comparison: 1

// Java code to demonstrate
// compareTo() function of Date class

import java.util.Date;

public class GfG {
    // main method
    public static void main(String[] args)
    {

        // creating a date of object
        // stospecified datent date
        Date currentDate = new Date();

        System.out.println("Date 1: " + currentDate);

        // specifiedDate is assigned to null.
        Date specifiedDate = null;

        System.out.println("Date 2: " + specifiedDate);

        System.out.println("Passing null as parameter: ");
        try {
            // throws NullPointerException
            System.out.println(currentDate
                                   .compareTo(specifiedDate));
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Output:

Date 1: Wed Jan 02 08:18:02 UTC 2019
Date 2: null
Passing null as parameter: 
Exception: java.lang.NullPointerException