How to avoid add elements to an ArrayList in Java once a specified limit is reached?

To avoid adding elements to an ArrayList in Java once a specified limit is reached, you can create a custom class that wraps around ArrayList and enforces the size limit. This custom class will control the behavior of the ArrayList by preventing the addition of new elements beyond the specified limit.

Here's a step-by-step guide to implement such a custom class:

1. Define the Custom Class

Create a custom class that encapsulates an ArrayList and includes logic to enforce the size limit.

2. Implement Methods to Control Access

Override methods related to adding elements to ensure that the limit is enforced.

Example Implementation

Here’s a sample implementation of a custom LimitedArrayList class:

public class LimitedArrayList<E> {

    private final List<E> list;

    private final int limit;

     public LimitedArrayList(int limit) {

        this.list = new ArrayList<>();

        this.limit = limit;

    }

     // Add an element to the list if the size is within the limit

    public boolean add(E element) {

        if (list.size() >= limit) {

            throw new IllegalStateException("Cannot add more elements: limit reached");

        }

        return list.add(element);

    }

    // Add all elements from a collection if it does not exceed the limit

    public boolean addAll(Collection<? extends E> c) {

        if (list.size() + c.size() > limit) {

            throw new IllegalStateException("Cannot add elements: limit would be exceeded");

        }

        return list.addAll(c);

    }

   }

Usage Example

Here’s how you can use the LimitedArrayList class:

public class Main {

    public static void main(String[] args) {

        // Create a LimitedArrayList with a limit of 5 elements

        LimitedArrayList<String> limitedList = new LimitedArrayList<>(5);

         // Add elements to the list

        try {

            for (int i = 1; i <= 6; i++) {

                limitedList.add("Element " + i);

                System.out.println("Added: Element " + i);

            }

        } catch (IllegalStateException e) {

            System.out.println(e.getMessage());  // Outputs: Cannot add more elements: limit reached

        }

         // Print the final list

        System.out.println("Final List: " + limitedList);

    }

}