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Java GregorianCalendar roll() Method with Example

GregorianCalendar Class roll() method: Here, we are going to learn about the roll() method of GregorianCalendar Class with its syntax and example.
Submitted by Preeti Jain, on February 15, 2020

GregorianCalendar Class roll() method

Syntax:

    public void roll(int fi, boolean status);
    public void roll(int fi, int amt);

• roll() method is available in java.util package.
• roll(int fi, boolean status) method is used to roll up or down a single quantity of time on the given time field (fi).
• roll(int fi, int amt) method is used to roll up or down the given time field (fi) with the given amt (amount) of time.
• These methods may throw an exception at the time of rolling the given field (fi).
  IllegalArgumentException: This exception may throw when the given field (fi) is not in a range in non-lenient mode.
• These are non-static methods, so it is accessible with the class object and if we try to access these methods with the class name then we will get an error.

Parameter(s):

• In the first case, roll(int fi, boolean status)
  • int fi – represent the calendar field.
  • boolean status – sets true when the given field (fi) roll up otherwise it sets false.
• In the first case, roll(int fi, int amt)
  • int fi – represent the calendar field.
  • int amt – represents the amount(amt) to add or substract to field (positive amt to add & negative amt to substract).

Return value:

In both the cases, the return type of the method is void, it does not return anything.

Example:

// Java program is to demonstrate the example of
// roll() method of GregorianCalendar

import java.util.*;

public class RollOfGregorianCalendar {
    public static void main(String[] args) {
        // Instantiating a GregorianCalendar object
        GregorianCalendar g_ca = (GregorianCalendar) GregorianCalendar.getInstance();

        // Display current GregorianCalendar
        System.out.println("g_ca.getTime(): " + g_ca.getTime());

        // By using roll(int,boolean) method is to
        // up a single unit of the given field if
        // boolean sets to true
        g_ca.roll(GregorianCalendar.YEAR, true);

        // Display Updated GregorianCalendar
        System.out.println("g_ca.roll(GregorianCalendar.YEAR, true): " + g_ca.getTime());

        // By using roll(int,int) method is to up
        // or down the given field with the given
        // amount of time
        g_ca.roll(GregorianCalendar.MONTH, 5);

        // Display Updated Calendar
        System.out.println("g_ca.roll(GregorianCalendar.MONTH, 5): " + g_ca.getTime());
    }
}

Output

g_ca.getTime(): Sat Feb 15 12:41:19 GMT 2020
g_ca.roll(GregorianCalendar.YEAR, true): Mon Feb 15 12:41:19 GMT 2021
g_ca.roll(GregorianCalendar.MONTH, 5): Thu Jul 15 12:41:19 GMT 2021