Java Collections emptyIterator() Method with Examples

The Collections.emptyIterator() method in Java returns an immutable empty Iterator that contains no elements. It is useful when a method needs to return an Iterator but there are no elements to iterate over, avoiding the need to return null.

• The iterator contains no elements, so hasNext() always returns false.
• Helps prevent NullPointerException by returning an empty iterator instead of null.

import java.util.*;

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

        Iterator<String> iterator = Collections.emptyIterator();

        System.out.println(iterator.hasNext());
    }
}

false

Explanation: The iterator is empty, so it contains no elements and hasNext() returns false.

Syntax:

public static <T> Iterator<T> emptyIterator()

• Parameters: This method does not accept any parameters.
• Return Value: Returns an empty Iterator containing no elements.
• Exceptions: This method does not throw any exceptions.

Example: Creating an Empty Iterator

import java.util.*;

public class GFG {

    public static void main(String[] args) {

        // Create an empty iterator
        Iterator<String> iterator =
                Collections.emptyIterator();

        System.out.println(iterator.hasNext());
    }
}

false

Explanation: The iterator is empty, so hasNext() returns false, indicating that there are no elements to iterate over.

Example: Iterating Over an Empty Iterator

import java.util.*;

public class GFG {

    public static void main(String[] args) {

        // Create an empty iterator
        Iterator<String> iterator =
                Collections.emptyIterator();

        while (iterator.hasNext()) {
            System.out.println(iterator.next());
        }

        System.out.println("Iterator is empty.");
    }
}

Iterator is empty.

Explanation: Since the iterator contains no elements, the while loop is never executed, and the program directly prints "Iterator is empty."

Related Methods

Advantages

• Returns a safe empty Iterator instead of null.
• Prevents NullPointerException in iterator-based code.
• Reusable and memory-efficient.
• Useful when implementing APIs that return an Iterator.