Скачать или смотреть Traversing Lists and Custom Types in Java

Java includes both an Array and an ArrayList class. They're each "collections of multiple items", so to speak, but they're also very different. An ArrayList can fluctuate in size as things are added or removed. A single ArrayList is also capable of holding a variety of different types of objects.

Java ArrayList
ArrayList is an ordered sequence of elements. It is dynamic and resizable. It provides random access to its elements. Random access means that we can grab any element at constant time. An ArrayList automatically expands as data is added. Unlike simple arrays, an ArrayList can hold data of multiple data types. It permits all elements, including null.