The Bridge pattern splits an abstraction from its implementation into two separate class hierarchies connected by composition, so each can evolve independently. In large systems this decoupling is what keeps a growing codebase manageable.
Key Points: • Abstraction and implementation can change independently without ripple effects across the codebase. • New implementations can be added without touching existing abstraction classes, following the open/closed principle. • It avoids a combinatorial explosion of subclasses that would result from mixing variations through inheritance alone. • It supports runtime swapping of the implementation object. • It improves testability since abstractions can be tested against mock implementations.
Example: A cross-platform reporting module might define a Report abstraction that delegates rendering to a Renderer implementation, with separate PdfRenderer and HtmlRenderer classes; adding a new output format only means adding a new Renderer, not touching Report subclasses.
Interview Tip: A concise interview answer is:
"In large systems the Bridge pattern's main benefit is decoupling an abstraction from its implementation so both can grow independently, which avoids a subclass explosion and lets you add new implementations without touching existing abstraction code."