Difference Between List, Set, and Map in Java

Java has a java.util package that consists of a Collection interface. This interface has many sub-interfaces and classes like List, Set, and Map. In this article, we will learn the difference between List, Set, and Map.

What is List Interface?

Java has a Collection interface and List is the sub-interface of Collection. This interface consists of methods like insert, update, delete, and search. Developers are also allowed to insert null elements.

List Interface Example

The List interface can be found in the java.util package. An example of a List is given below ?

import java.util.*;
public class ListExample {
   public static void main (String args[]) {
      List<String> mylist = new ArrayList<>();
      mylist.add("James Bond");
      mylist.add("Superman");
      mylist.add("Spiderman");
      for(String superhero : mylist)
         System.out.println(superhero);
   }
}

Output

James Bond
Superman
Spiderman

What is a Set Interface?

Set is an interface which extends the Collection interface. It is available in the java.util package. This is an interface in which duplicate items are not considered and will be ignored when the output is printed.

Set Interface Example

Here is a simple example of the Set interface.

import java.util.*;
public class MySet {
   public static void main (String args[]) {
      Set<String> setmyalp = new HashSet<String>();
      setmyalp.add("A");
      setmyalp.add("B");
      setmyalp.add("C");
      setmyalp.add("D");
      setmyalp.add("E");
      System.out.println(setmyalp);
   }
}

Output

[A, B, C, D, E]

What is Map Interface?

The map is an interface which can be found in the java.util package. This is an interface which is used to match a key with a value. After storing the key and value in the Map interface, users can just use the key to get its value.

Map Interface Example

Here is an example of using the Map interface.

import java.util.*;
public class MyMap {
   public static void main (String args[]) {
      Map<String, String> mapvalue =new HashMap<String, String>();
      mapvalue.put("Fruit" , "Apple");
      mapvalue.put("Vegetable" , "Potato");
      mapvalue.put("Nut" , "Groundnut");
      for(Map.Entry me : mapvalue.entrySet()) {
         System.out.println(me.getKey() + " " + me.getValue());
      }
   }
}

Output

Fruit Apple
Nut Groundnut
Vegetable Potato

Difference between List, Set, and Map Interfaces in Java

List, Set, and Map interfaces belong to the java.util package and they extend the Collection Interface. There are a few differences between them which can be found in the table below ?

Conclusion

List, Set, and Map interfaces belong to the java.util package and they extend the Collection interface. List allows duplicate values and the insertion of values is ordered. Set and Map interfaces do not allow duplicate values and the insertions are not organized. All these interfaces are used for different purposes.

FAQs on List Vs. Set Vs. Map

1. To which package do List, Set, and Map interfaces belong?

List, Map, and Set interfaces belong to the java.util package. They extend the Collection interface. The List and Set interfaces are used to add, remove, or update elements while the Map interface follows a key-value pair.

2. How many null values can be inserted in all these interfaces?

Any amount of null values can be inserted in the List interface while only one null value is supported by Set. In the Map interface, the key can only have one null but the value can have any number of null.

3. Which classes implement the List interface?

List interface can be implemented by

• ArrayList
• LinkedList

4. Which interface allows duplicate values to be inserted?

Duplicate values can be inserted in the List interface but this is not the case with the Set and Map interfaces.

5. Which of the interfaces has get method to retrieve elements at a particular index?

Only the List interface has the get() method to retrieve elements from a particular index.