How to check the Java list size?

The Java List interface provides a size() method to check the current number of elements in the list. The size updates automatically as elements are added or removed.

Syntax

int size()

Returns the number of elements in the list. If the list contains more than Integer.MAX_VALUE elements, it returns Integer.MAX_VALUE.

Example

The following example shows how the list size changes after adding and removing elements ?

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class CollectionsDemo {
    public static void main(String[] args) {
        List<Integer> list = new ArrayList<>(Arrays.asList(1, 2, 3, 4));
        System.out.println("List: " + list);
        System.out.println("List Size: " + list.size());

        // Add elements
        list.add(5);
        list.add(6);
        list.add(7);
        System.out.println("List: " + list);
        System.out.println("List Size: " + list.size());

        // Remove element at index 5 (value 6)
        list.remove(5);
        System.out.println("List: " + list);
        System.out.println("List Size: " + list.size());
    }
}

The output of the above code is ?

List: [1, 2, 3, 4]
List Size: 4
List: [1, 2, 3, 4, 5, 6, 7]
List Size: 7
List: [1, 2, 3, 4, 5, 7]
List Size: 6

Conclusion

Use list.size() to get the current number of elements in any Java List. The size reflects the actual element count and updates dynamically as elements are added or removed. To check if a list is empty, you can also use list.isEmpty() which is equivalent to list.size() == 0.