Java: Invariants and Validation

Invariants define consistent rules for valid object states.

Invariants are fundamental for ensuring objects always remain in a valid state. They act as rules that define valid conditions, such as a product having a non-negative price. Without invariants, objects could easily fall into inconsistent or invalid states, leading to unreliable behavior or errors. For instance, if an Order object allows negative quantities, it could disrupt inventory management in an e-commerce system.