encapsulation

To prevent external mutation of internal object state, use private fields for data and expose behavior through public methods. This ensures all state changes occur through validated methods, maintaining invariants and supporting safe code evolution.

The best way to protect class invariants is to hide internal data via private fields and route all mutations through controlled public methods. This prevents external callers from directly changing fields and breaking object integrity.

Getters and setters should return copies of collections to avoid aliasing, which occurs when external callers hold direct references to internal data. Returning copies or read-only views preserves invariants by preventing unvalidated external state changes.

You need to use encapsulation practices in typical object-oriented codebases where invariants must be maintained. It is required when internal object state must be protected from direct external access and all mutations need to occur through validated methods.