Bnb.java

package com.mywonderfulbnb.bnb.definition

final class Bnb {
  private BnbId bnbId;
  private OwnerId ownerId;
  private Name name;

  public Bnb(BnbId bnbId, OwnerId ownerId, Name name) {
    this.bnbId = bnbId;
    this.ownerId = ownerId;
    this.name = name;
  }
}

Bnbs.java

package com.mywonderfulbnb.bnb.definition

interface Bnbs {
  void save(Bnb bnb);
}

Service.java

package com.mywonderfulbnb.bnb.definition

final class Service {
  private Bnbs Bnbs;
  private ActivatedOwners activatedOwners;

  public Service(Bnbs bnbs, ActivatedOwners activatedOwners) {
    this.bnbs = bnbs;
    this.activatedOwners = activatedOwners;
  }

  public addBnb(UUID ownerUuid, UUID bnbUuid, String nameStr) {
    ownerId = new OwnerId(ownerUuid);
    bnbId = new BnbId(bnbUuid);
    name = new Name(nameStr);
    
    assertOwnerIsActivated(ownerId);
    
    bnb = new Bnb(bnbUuid, ownerId, name);
    
    this.bnbs.save(bnb);
  }
  
  private assertOwnerIsActivated(OwnerId ownerId) {
    itExists = activatedOwners.existsOneWithId(ownerId);
    
    if (!itExists) {
      throw new ActivatedOwnerNotFound(ownerId);
    }
  }
}