ActivatedOwnerNotFound.java

package com.mywonderfulbnb.bnb.definition

final class ActivatedOwnerNotFound extends Exception {
  private OwnerId ownerId;

  public ActivatedOwnerNotFound(OwnerId ownerId) {
    this.ownerId = ownerId;
  }
}

ActivatedOwners.java

package com.mywonderfulbnb.bnb.definition

interface ActivatedOwners {
  bool existsOneWithId(OwnerId ownerId);
}

Service.java

package com.mywonderfulbnb.bnb.definition

final class Service {
  private ActivatedOwners activatedOwners;

  public Service(ActivatedOwners activatedOwners) {
    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);
  }
  
  private assertOwnerIsActivated(OwnerId ownerId) {
    itExists = activatedOwners.existsOneWithId(ownerId);
    
    if (!itExists) {
      throw new ActivatedOwnerNotFound(ownerId);
    }
  }
}