ArrayList<Integer>

An ArrayList is a class in Java that provides a dynamic array implementation. It is part of the Java Collections Framework and is used to store a collection of objects. The ArrayList class is a generic class that can be used to store objects of any type.

The ArrayList<Integer> denotes an ArrayList that can only store objects of the Integer type. This is achieved through the use of Java generics, which allows the type of objects stored in a collection to be specified at compile time.

Here's an example of how to create an ArrayList<Integer>:

ArrayList<Integer> myList = new ArrayList<Integer>();

This creates a new ArrayList that can store objects of the Integer type. The ArrayList is initially empty, and elements can be added using the `add()` method:

myList.add(1);
myList.add(2);
myList.add(3);

This adds the integers 1, 2, and 3 to the ArrayList. The `size()` method can be used to get the number of elements in the ArrayList:

int size = myList.size(); // size is now 3

Elements can be retrieved from the ArrayList using the `get()` method:

int element = myList.get(0); // element is now 1

This retrieves the first element in the ArrayList (at index 0) and stores it in the `element` variable.