Java 25 (LTS) reference · List and ArrayList Methods

Java List.of() Method

Create an immutable list from values. Adding or removing later throws UnsupportedOperationException.

Java 25 (LTS) Since Java 9

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Syntax

List.of(e1, e2, ...)

Parameters

Parameter	Description
`elements` E...	The values (no nulls).

Return value

An unmodifiable List<E>.

Examples

An immutable list

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<String> days = List.of("Mon", "Tue", "Wed");
        System.out.println(days + " size " + days.size());
        try {
            days.add("Thu");
        } catch (UnsupportedOperationException e) {
            System.out.println("List.of lists are immutable");
        }
    }
}

Output

[Mon, Tue, Wed] size 3
List.of lists are immutable

Run this on your computer — see “Get Started” for setup.

Make a mutable copy

import java.util.*;

public class Main {
    public static void main(String[] args) {
        List<Integer> fixed = List.of(3, 1, 2);
        List<Integer> copy = new ArrayList<>(fixed);  // a mutable copy
        copy.add(4);
        System.out.println(copy);
    }
}