How is an element added to the middle of an array in the ArrayList structure?

In the ArrayList data structure in Java, adding an element in the middle of the array occurs as follows:

1. It checks whether there is enough space in the internal array for the new element. If not, the array is enlarged (usually by copying to a new array with a larger size).
2. All elements from the insertion position to the end are shifted one position to the right to make space.
3. The new element is inserted into the freed position.

Example code:

ArrayList<String> list = new ArrayList<>();
list.add("A");
list.add("B");
list.add("D");

// Insert "C" at position 2 (counting from 0)
list.add(2, "C");

System.out.println(list); // Outputs [A, B, C, D]

It is important to understand that inserting in the middle of an ArrayList is an operation with linear complexity O(n), as it requires shifting elements.