What is the main difference between an Array and an ArrayList?

The main difference between an Array and an ArrayList is that arrays have a fixed size, while ArrayLists can grow dynamically. When you create an array, you must specify its size at the time of creation, and this size cannot be changed once the array is initialized. This means if you need to add more elements than the initial size of the array, you cannot do this without creating a new array with a larger size and copying the elements over.

On the other hand, ArrayLists are part of the Java Collections Framework, and they are designed to be more flexible. They can grow and shrink in size as you add or remove elements. This dynamic resizing is handled automatically by the ArrayList, providing more convenience when working with lists of unknown or changing size.

This distinction between fixed and dynamic sizes is crucial, especially for developers who need to manage collections of elements efficiently. With ArrayLists, you can easily manage size without worrying about going over a predefined limit, making them suitable for scenarios where the number of elements is not known in advance.