How to Reverse an arrayList in Java using Collections and Recursion ?

To reverse a List in Java e.g. ArrayList or LinkedList, you should always use
the Collections.reverse() method. It's safe and tested and probably



perform better than the first version of the method you write to reverse an ArrayList in Java


In this tutorial, I'll show you how to reverse an ArrayList of String using recursion as well. 








In a recursive algorithm, a function calls itself to do the job. After each pass problem 

becomes smaller and smaller until it reaches to the base case.



In order to reverse a List using recursion our base case is a list of one element. If 

your list contains one element then the reverse of that list is the list itself, so 

just return it. Now, on each pass we need to program reaches to base case and starts 

winding down, we end up all the add the last element on the list into a new list 

called reversed. 






import java.util.ArrayList;



import java.util.Collections;



import java.util.List;



public class TestSolution {





public static void main(String args[])

{





List books = new ArrayList<>(); 



books.add("Beautiful Code");



books.add("Clean Code");



books.add("Working Effectively with Legacy Code");



System.out.println("Original order of List: " + books);



Collections.reverse(books); 



System.out.println("The reversed List: " + books);



//Now, let's try to reverse a List using recursion List





output = reverseListRecursively(books); 



System.out.println("Reversed list reversed again:

" + output); } 



/** * A recursive algorithm to reverse a List in Java * *

@param list * @return */



private static List reverseListRecursively(Listlist) {



if (list.size() <= 1) 

{ 



     return list;

}



List reversed = new ArrayList<>();



reversed.add(list.get(list.size() - 1));

//last element



reversed.addAll(reverseListRecursively(list.subList(0, list.size() - 1)));



return reversed; 



      }



 } 







Output 

Original order of List: [Beautiful Code, Clean Code, Working Effectively with Legacy Code] 

The reversed List: [Working Effectively with Legacy Code, Clean Code, Beautiful Code]