At what stage do data collections usually start to be created and used in programming?

Data collections are usually created and used during the design and implementation phase of the application's business logic, when it is necessary to store and process groups of related objects. For example, when developing an application to manage a list of users or products, there is an immediate need to use collections to store these objects.

At the code level, collections are used:

• When loading data from a database or external sources.
• For temporary storage and processing of data in memory.
• To pass groups of data between methods and layers of the application.

In Java, interfaces and classes from the java.util package are often used for this purpose, such as List, Set, Map, ArrayList, HashSet, etc.