Why Classes Should Not Be Too Long and How to Refactor Them

When a class grows to hundreds of lines and exposes dozens of public methods, it becomes hard to read and maintain; even the original author may struggle to understand it after a short time.

Long classes often contain redundant code created by copy‑and‑paste, leading to duplicated logic that must be updated in many places, and they usually suffer from excessive responsibilities that break the Single Responsibility Principle.

These problems cause scattered changes (fan‑in/fan‑out), make extensions cumbersome, and increase the risk of bugs during testing and operations.

The article proposes practical refactoring strategies: first, extract redundant code into separate methods; then, rename methods with clear verb‑noun names; next, move fields and methods to more appropriate classes, or create new classes when no suitable target exists.

IntelliJ IDEA’s built‑in refactoring tools are demonstrated: using Ctrl+Alt+M to extract methods, Ctrl+F6 to change method signatures, and the Refactor → Move action to relocate members or functions.

When extracting a class, the author advises selecting members that are most frequently used together, ensuring the new class respects cohesion and the “intimacy” principle.

Finally, the article warns against creating unnecessary parameter objects and emphasizes that successful refactoring reduces code duplication, improves readability, and simplifies future extensions.