A collection is just what its name implies: a collection of objects. Collections make it easy to work with large numbers of similar objects by enabling you to create code that performs iterative processing on items within the collection. Iterative processing is an operation that uses a loop to perform actions on multiple objects, rather than writing the operative code for each object. In addition to containing an indexed set of objects, collections also have properties and may have methods. Figure 3.8 illustrates the structure of a collection.
Figure 3.8. Collections contain sets of like objects, and they have their own properties and methods.
Continuing with the Dog/Pet object metaphor, think about what an Animals collection ...