Java ArrayList class uses a `dynamic array` for storing the elements. It is like an array, but there is no size limit. We can add or remove elements anytime. So, it is much more flexible than the traditional array. It is found in the `java.util` package. It is like the `Vector` in C++.

The ArrayList in Java can have the duplicate elements also. An ArrayList class extends `AbstractList` class which implements `List interface`. The List interface extends the `Collection` and `Iterable interfaces` in hierarchical order.