Arrays.asList() vs. List.of() in Java

By Atul Rai | Last Updated: October 15, 2024 Previous

List.of and Arrays.asList are both used to create lists in Java, but they have some differences:

1. List.of()

• Introduced in Java 9.
• Creates an immutable list.
• Does not allow null elements.
• Returns a list with a fixed size.

2. Arrays.asList()

• Available since Java 1.2.
• Creates a mutable list backed by an array.
• Allows null elements.
• The size of the list is fixed, but the elements can be changed.

Example

// Using List.of
List<String> immutableList = List.of("a", "b", "c");
// immutableList.add("d"); // This will throw UnsupportedOperationException

// Using Arrays.asList
List<String> mutableList = Arrays.asList("a", "b", "c");
mutableList.set(0, "z"); // This is allowed
// mutableList.add("d"); // This will throw UnsupportedOperationException

Similar Post: Java 9- Creating Collection using Factory Method of(…)

3. Summary

• Use List.of for creating immutable lists with no null elements.
• Use Arrays.asList for creating mutable lists that allow null elements but have a fixed size.

4. References

1. Arrays.asList() – JavaDoc
2. List.of() – JavaDoc