Code Recipes Blog

In this post under Java, I will show with example how to convert a collection to unmodifiable list.

To convert a collection to an immutable List, we take help of “List” interface static method “copyOf”.

Below is the complete code for your reference.

Main class

1  package core.collection;
2  
3  import java.util.HashSet;
4  import java.util.List;
5  import java.util.Set;
6  
7  public class CollectionToListConversionDemo {
8      public static void main(String[] args) {
9          Set<Integer> integerSet = new HashSet<>(0);
10         integerSet.add(1);
11         integerSet.add(2);
12         integerSet.add(3);
13         integerSet.add(4);
14         integerSet.add(5);
15 
16         List<Integer> integerList = List.copyOf(integerSet);
17         System.out.println(integerList);
18     }
19 }

In the above code, at line 9 I create a set of type parameter “Integer” named “integerSet”.

From line 10 to 14, I populate the set.

At line 16, I call the “List” interface static method “copyOf” and pass the set as an argument. The return value is a immutable list.

At line 17, I print the elements of the list.

In this way, we can convert a collection to immutable list.