Question

How do you do reverse arrayList? using recursion? displaying it for example

Normal array list 1 2 3 4 5 6 7

reverse array list 7 6 5 4 3 2 1

Answer 1

import java.util.ArrayList;

import java.util.Collections;

import java.util.List;

class ReverseArrayList

{

public static void main(String args[])

{

ArrayList<String> a1 = new ArrayList<String>();

a1.add("1");

a1.add("2");

a1.add("3");

a1.add("4");

a1.add("5");

a1.add("6");

a1.add("7");

System.out.println("\nNormal ArrayList : " + a1);

List<String> output = reverseListRecursively(a1);

System.out.println("\nReversed ArrayList : " + output);

System.out.println();

}

  

private static List<String> reverseListRecursively(List<String> list)

{

if (list.size() <= 1)

{

return list;

}

List<String> reversed = new ArrayList<>();

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

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

return reversed;

}

}

s c:\Users\u se r \Desktop> ]avac Re verseArrayList,java PS C:\Users\user Desktop> java ReverseArrayList Normal ArrayList [i, 2, 3, 4, 5, 6, 7] Reversed ArrayList [7, 6, 5, 4, 3, 2, 1] PS C:\Users userDesktop> - O Type here to search