Difference : List Vs Set

List and Set differs based on the following parameters.

1.       Duplicate Object

List allows duplicate elements to be stored in it.

Set doesn’t allow duplicate element. All the element needs to be unique.

2.       Order Maintenance

List generally maintains the insertion order.

In set maintenance of insertion order depends on the implementing class. (HashSet-> order not guaranteed, LinkedHashSet-> Order is maintained)

3.       Null value

In List, one can store unlimited null values

In Set, only one null value is permitted.

4.       Implementations

ArrayList class, LinkedList class and Vector class implements List interface.

HashSet class, LinkedHashSet class and TreeSet class implements Set interface.

5.       Traversal

You can use both ListIterator and Iterator to traverse elements in List.

You cannot use ListIterator to iterate Set. To traverse Set use Iterator.

Example

package collection;

import java.util.ArrayList;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

public class ListandSet {

      public static void main(String[] args) {

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

            arrayList.add("A");

            arrayList.add("B");

            arrayList.add("A");

            arrayList.add("C");

            arrayList.add("D");

            System.out.println("List elements:"+ arrayList);

           

            Set<String> set = new HashSet<String>();

            set.add("A");

            set.add("B");

            set.add("A");

            set.add("C");

            set.add("D");

            System.out.println("Set elements:"+ set);

      }

}

Output:

List elements:[A, B, A, C, D]
Set elements:[A, B, C, D]