Find duplicate value in array list and print the duplicated value

Using java 8

package com.logical.programming.prime;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.stream.Collectors;

public class Example {

 public static void main(String[] args) {

  ArrayList<String> list = new ArrayList();
  list.add("1");
  list.add("2");
  list.add("2");
  list.add("3");
  list.add("4");
  list.add("4");
  list.add("5");
  list.add("5");

  HashSet set = new HashSet();

  List l1 = list.stream().filter(n -> !set.add(n)).collect(Collectors.toList());
  System.out.println(set); o/p [1, 2, 3, 4, 5]
  System.out.println(l1); o/p [2, 4, 5]

 }

}

[1, 2, 3, 4, 5]
[2, 4, 5]

duplicate element

Second Method Using Java 7

package com.logical.programming.prime;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class Example {

 public static void main(String[] args) {

  ArrayList<String> list = new ArrayList();
  list.add("1");
  list.add("2");
  list.add("2");
  list.add("3");
  list.add("4");
  list.add("4");
  list.add("5");
  list.add("5");

//  HashSet set = new HashSet();
//
//  List l1 = list.stream().filter(n -> !set.add(n)).collect(Collectors.toList());
//  // System.out.println("Output for set" + set);
//  // System.out.println("Dublicate list" + l1);

  Set set = new HashSet();
  List list2 = new ArrayList<>();

  for (int i = 0; i < list.size(); i++) {

   if (set.contains(list.get(i))) {

//    System.out.println("DUblicate" + list.get(i));
    list2.add(list.get(i));

   } else {
    set.add(list.get(i));
   }
  }
  System.out.println(set);
  System.out.println(list2);

 }

}

o/p
[1, 2, 3, 4, 5]
[2, 4, 5]