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Java Collections rotate() Method with Example

Collections Class rotate() method: Here, we are going to learn about the rotate() method of Collections Class with its syntax and example.
Submitted by Preeti Jain, on February 04, 2020

Collections Class rotate() method

• rotate() method is available in java.util package.
• rotate() method is used to rotate the List(l) elements by the given distance (dis).
• rotate() method is a static method, so it is accessible with the class name and if we try to access the method with the class object then we will not get an error.
• rotate() method may throw an exception at the time of rotating the list elements.
  UnsupportedOperationException: This exception may throw when the given parameter list(l) un-support set operation.

Syntax:

    public static void rotate(List l, int dis);

Parameter(s):

• List l – represents the list(l) to be rotated.
• int dis – represents the distance to rotate the list elements.

Return value:

The return type of this method is void, it returns nothing.

Example:

// Java program is to demonstrate the example of
// rotate(List l, int dis) method of Collections

import java.util.*;

public class RotateOfCollections {
    public static void main(String args[]) {
        // Instatiates a array list object
        List < Integer > arr_l = new ArrayList < Integer > ();

        // Declare distance for rotating purpose
        int dis = 4;

        // By using add() method is to add
        // objects in an array list 
        arr_l.add(10);
        arr_l.add(20);
        arr_l.add(30);
        arr_l.add(40);
        arr_l.add(50);
        arr_l.add(60);
        arr_l.add(70);
        arr_l.add(80);
        arr_l.add(90);
        arr_l.add(100);

        // Display ArrayList
        System.out.println("Array List: " + arr_l);

        // By using rotate() method is to
        // rotate the order of elements at 
        // the given distance
        Collections.rotate(arr_l, dis);

        // Display rotatable ArrayList
        System.out.println("Collections.rotate(arr_l,dis): " + arr_l);
    }
}

Output

Array List: [10, 20, 30, 40, 50, 60, 70, 80, 90, 100]
Collections.rotate(arr_l,dis): [70, 80, 90, 100, 10, 20, 30, 40, 50, 60]