Understanding Initial Size in ArrayLists

In Java, ArrayLists are dynamic arrays that can grow and shrink as needed. One can specify the initial size of an ArrayList using the constructor new ArrayList(10), where 10 represents the desired capacity.

However, setting an initial size does not grant immediate access to the allocated space. Unlike traditional arrays, ArrayLists are initialized with zero elements, regardless of the specified capacity. This raises the question of why one should set an initial size if they cannot access the space allocated.

The answer lies in the distinction between the ArrayList's size and capacity. Size refers to the number of elements actually present in the ArrayList, while capacity determines how many elements the ArrayList can hold before it needs to allocate more memory.

By setting the initial capacity, you are essentially informing the ArrayList that it should be prepared to store a specific number of elements without having to immediately allocate that much memory unnecessarily. This can improve performance, especially when you expect to add a significant number of elements to the ArrayList.

To access the elements added to the ArrayList, you need to use loops or other methods to manually add the desired number of elements. Only then can you access and modify those elements using the specified indices.