ArrayList

Java’s ArrayList is a Generic class that implements the List ADT. ArrayList allows a collection of objects to be stored inside a dynamic, resizable array.

It belongs to the java.util Java Package.

ArrayList cannot be used with primitives, so we need to use wrapper classesinstead!

Since it is a generic class, it must be supplied a type argument when initialised:

import java.util.ArrayList;
 
ArrayList<int> intList = new intList<>(); //Compile-time error
//Creates a new ArrayList that can only hold Integers
ArrayList<Integer> IntList = new ArrayList<>();

• It uses an Array as an instance variable
• Can be accessed via index, but not by [] notation. I.e. we can’t do IntList[3], instead we need to do IntList.get(3)
• ArrayList does not dynamically shrink, we need to use the method trimToSize() which reduces the array ‘capacity’.