Sometimes deciding which object to create is a job in itself. The Factory pattern gives that decision one home so the rest of your code stays simple.

A growing if/else chain that switches on a type is a design pattern in disguise. Here's how the Strategy pattern turns it into small, swappable pieces.

Inheritance looks tidy until the hierarchy fights you. Here's the concrete point where 'is-a' breaks and 'has-a' scales, shown with real code.