An ArrayList stores a variable number of objects. This is similar to making an array of objects, but with an ArrayList, items can be easily added and removed from the ArrayList and it is resized dynamically. This can be very convenient, but it's slower than making an array of objects when using many elements. Note that for resizable lists of integers, floats, and Strings, you can use the Processing classes IntList, FloatList, and StringList.

An ArrayList is a resizable-array implementation of the Java List interface. It has many methods used to control and search its contents. For example, the length of the ArrayList is returned by its size() method, which is an integer value for the total number of elements in the list. An element is added to an ArrayList with the add() method and is deleted with the remove() method. The get() method returns the element at the specified position in the list. (See the above example for context.)

For a list of the numerous ArrayList features, please read the Java reference description.