Java Program to Rotate Elements of a List

The List extends Collection and declares the behavior of a collection that stores a sequence of elements. The Collection is a framework that provides architecture to store and manipulate the group of objects. Java Collections can achieve all the operations that you perform on a data such as searching, sorting, insertion, manipulation, and deletion.

In this article, we will learn to rotate elements of a list in Java. Rotating a list means shifting the elements of the list either to the left or to the right.

Following are the ways to rotate elements of a list in Java:

• Using Collections
• Using Loops
• Using Streams

Rotate Elements of a List Using Collections

We have a built in method in the Collections class called Collections.rotate() that can be used to rotate the elements of a list. This method takes two parameters: the list to be rotated and the distance by which the elements should be rotated.

Example

Below is an example of rotating elements of a list using Collections. Here we will rotate the elements of a list to the right by 2 positions:

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class RotateList {
   public static void main(String[] args) {
      List<String> list = new ArrayList<>();
      list.add("Java");
      list.add("Python");
      list.add("Scala");
      list.add("C++");
      
      System.out.println("Original List: " + list);
      
      Collections.rotate(list, 2);
      
      System.out.println("Rotated List: " + list);
   }
}

Output

Following is the output of the above code:

Original List: [Java, Python, Scala, C++]
Rotated List: [Scala, C++, Java, Python]

Rotate Elements of a List Using Loops

We can also rotate elements of a list using loops. We can create a new list and add elements from the original list based on the rotation distance.

Example

Below is an example of rotating elements of a list using loops. Here we will rotate the elements of a list to the left by 2 positions:

import java.util.ArrayList;
import java.util.List;
public class RotateListUsingLoops {
   public static void main(String[] args) {
      List<String> list = new ArrayList<>();
      list.add("Java");
      list.add("Python");
      list.add("Scala");
      list.add("C++");
      
      System.out.println("Original List: " + list);
      
      int distance = 2;
      List<String> rotatedList = new ArrayList<>();
      
      for (int i = distance; i < list.size(); i++) {
         rotatedList.add(list.get(i));
      }
      
      for (int i = 0; i < distance; i++) {
         rotatedList.add(list.get(i));
      }
      
      System.out.println("Rotated List: " + rotatedList);
   }
}

Output

Following is the output of the above code:

Original List: [Java, Python, Scala, C++]

Rotated List: [Scala, C++, Java, Python]

Rotate Elements of a List Using Streams

Java Streams can also be used to rotate elements of a list. We can use the Stream API to manipulate the list and make rotation of the elements.

Example

Below is an example of rotating elements of a list using Streams. Here we will rotate the elements of a list to the right by 2 positions:

import java.util.ArrayList;
import java.util.List;
import java.util.stream.Collectors;
public class RotateListUsingStreams {
   public static void main(String[] args) {
      List<String> list = new ArrayList<>();
      list.add("Java");
      list.add("Python");
      list.add("Scala");
      list.add("C++");
      
      System.out.println("Original List: " + list);
      
      int distance = 2;
      List<String> rotatedList = new ArrayList<>();
      
      rotatedList = list.stream()
         .skip(list.size() - distance)
         .collect(Collectors.toList());
      
      rotatedList.addAll(list.stream()
         .limit(list.size() - distance)
         .collect(Collectors.toList()));
      
      System.out.println("Rotated List: " + rotatedList);
   }
}

Output

Following is the output of the above code:

Original List: [Java, Python, Scala, C++]
Rotated List: [Scala, C++, Java, Python]