Calendar compareTo() Method in Java with Examples

The add(Calendar Calendar2) method of Calendar class is used to compare the time values or the millisecond offsets of this Calendar object with the passed Calendar object.

Syntax:

public int compareTo(Calendar Calendar2)

Parameters: The method takes one parameter Calendar2 of Calendar object type and refers to the object to be compared to this Calendar object.

Return Value: The method returns an integer value and can return any one of the following:

1. The method returns 0 if the passed argument is equal to this Calendar object.
2. The method returns 1 if the time of this Calendar object is more than the passed object.
3. The method returns -1 if the time of this Calendar object is less than the passed object.

Below programs illustrate the working of compareTo() Method of Calendar class:
Example 1:

// Java Code to illustrate compareTo() Method

import java.util.*;

public class CalendarClassDemo {
    public static void main(String args[])
    {
        // Creating a calendar object
        Calendar calndr1
            = Calendar.getInstance();

        // Creating another calendar object
        Calendar calndr2
            = new GregorianCalendar(2018, 12, 2);

        // Comparing the time
        int val = calndr1.compareTo(calndr2);

        // Displaying the result of comparison
        System.out.println("First"
                           + " comparison result is: "
                           + val);

        // Comparing the time
        val = calndr2.compareTo(calndr1);

        // Displaying the result of comparison
        System.out.println("Second"
                           + " comparison result is: "
                           + val);
    }
}

Output:

First comparison result is: 1
Second comparison result is: -1

Example 2:

// Java Code to illustrate compareTo() Method

import java.util.*;

public class CalendarClassDemo {
    public static void main(String args[])
    {
        // Creating a calendar object
        Calendar calndr1 = Calendar.getInstance();

        // Creating another calendar object
        Calendar calndr2 = Calendar.getInstance();

        // Comparing the time
        int val = calndr1.compareTo(calndr2);

        // Displaying the result of comparison
        System.out.println("The"
                           + " comparison result is: "
                           + val);
    }
}

Output:

The comparison result is: -1

Reference: https://docs.oracle.com/javase/7/docs/api/java/util/Calendar.html#compareTo(java.util.Calendar)