Collection

A number of objects such as all the emails currently in your inbox is called a collection. Do remember that class is a blueprint not the object itself where as collection is created with instances of each objects

This collection is of objects which are all instances of the same class (the class of emails).

A collection is a list which we can put into order using one or more of the properties of the objects in the collect.  Date order for example. 

We can count the number of items in a collection and we can find those which match some criteria (based on a property) such as “from my mother”.

We can assign an index number to each object (or element) in a collection.  For example the ‘first’, ‘second’, ‘seventeenth’ or ‘last’ item.