In your model example, you forgot to override hashCode as one should: https://stackoverflow.com/questions/2265503/why-do-i-need-to-override-the-equals-and-hashc

In your model example, you forgot to override hashCode as one should: https://stackoverflow.com/questions/2265503/why-do-i-need-to-override-the-equals-and-hashcode-methods-in-java https://stackoverflow.com/questions/2265503/why-do-i-need-to... EDIT: nvm, I completely missed it