Java Collections emptyListIterator() Method with Examples

The Collections.emptyList() method of the java.util.Collections class returns an immutable empty List. The returned list contains no elements and cannot be modified. Any attempt to add, remove, or update elements in the returned list results in an UnsupportedOperationException.

• Does not require creating a new ArrayList object.
• Generic method that works with any object type.
• Commonly used to return an empty list instead of null.

import java.util.*;

public class Main {
    public static void main(String[] args) {

        List<String> names = Collections.emptyList();

        if (names.isEmpty()) {
            System.out.println("No records found.");
        }
    }
}

No records found.

Explanation: This example uses Collections.emptyList() to safely return an empty list and checks whether it contains any elements using the isEmpty() method.

Syntax

public static final <T> List<T> emptyList()

• Parameters: This method does not accept any parameters.
• Return Value: Returns an immutable empty List of the specified type.
• Exception: UnsupportedOperationException: Thrown if an attempt is made to modify the returned empty list.

Example: Creating an Empty List using emptyList()

import java.util.*;

public class GFG {
    public static void main(String[] args) {

        // Create an immutable empty list
        List<String> list = Collections.emptyList();

        // Display the list
        System.out.println("Empty List: " + list);

        // Check its size
        System.out.println("Size: " + list.size());
    }
}

Empty List: []
Size: 0

Explanation: This example creates an immutable empty list using Collections.emptyList(). Since the list contains no elements, its size is 0.

Example: Attempting to Modify an Empty List

import java.util.*;

public class GFG {

    public static void main(String[] args) {

        // Create an immutable empty list
        List<Integer> list = Collections.emptyList();

        try {
            // Attempt to add an element
            list.add(10);
        }
        catch (UnsupportedOperationException e) {
            System.out.println("Exception: " + e);
        }
    }
}

Exception: java.lang.UnsupportedOperationException

Explanation: The list returned by Collections.emptyList() is immutable. Therefore, adding an element throws an UnsupportedOperationException.

Collections.emptyList() and new ArrayList<>()

Advantages of emptyList()

• Returns a reusable immutable empty list.
• Avoids unnecessary object creation.
• Safer than returning null from methods.
• Improves code readability and reliability.
• Supports generic type safety.