How to perform operations of Union and Intersection on two or more LinkedList in Java ?.

Program to demonstrate Union and Intersection of two LinkedList in Java

package com.hubberspot.collections.example;

import java.util.*;
import java.io.*;

public class LinkedListOperationsDemo
{
  static BufferedReader br = new BufferedReader
   (new InputStreamReader(System.in));

  public static void main(String args[]) throws IOException
  {
    LinkedList list1 = new LinkedList();
    LinkedList list2 = new LinkedList();
    LinkedList list3 = new LinkedList();
    LinkedList list4 = new LinkedList();
   
    int num1, num2;

    System.out.print("Enter no.of Elements in list 1:");
  
    num1 = Integer.parseInt(br.readLine());

    System.out.println("Enter Elements of list 1");
  
    for(int i=1; i <= num1; i++)
    {
      System.out.print("Enter Element "+i+": ");
      String element = br.readLine();
 
      if(!list1.contains(element))
 list1.add(element);
    }                                

    System.out.print("Enter no.of Elements in list 2:");
  
    num2 = Integer.parseInt(br.readLine());
  
    System.out.println("Enter Elements of list 2");
  
    for(int i=1; i <= num2; i++)
    {
      System.out.print("Enter Element "+i+": ");
      String element = br.readLine();
 
      if(!list2.contains(element))
 list2.add(element);
    }                                

    Collections.sort(list1);
    Collections.sort(list2);

    System.out.println("List 1:"+list1);
    System.out.println("List 2:"+list2);
     
    for(int i=0; i < list1.size(); i++)
      list3.add(list1.get(i));
  
    for(int i=0; i < list2.size(); i++)
      if(!list1.contains(list2.get(i)))
 list3.add(list2.get(i));
  
    System.out.println("Union: "+list3);
  
    for(int i=0; i < list1.size(); i++)
       list4.add(list1.get(i));
  
    list4.retainAll(list2);
  
    System.out.println("Intersection: "+list4);

   }
}

Output of the program :