Are there situations where working with multiple versions of a product simultaneously is required?

Yes, situations with working simultaneously on multiple versions of a product are quite common, especially in the following cases:

• Support for old versions: when it is necessary to fix bugs or release patches for already released versions, alongside developing new features in the main branch.

• Parallel development of new features: when different teams work on different versions of the product (for example, stable and experimental).

• Migration and updates: during a gradual transition from one version to another, when both versions need to operate in parallel for users.

To manage such situations in Java projects, version control systems (Git, SVN) with branching are often used, as well as build and deployment tools that support and run different versions of the product simultaneously.