Finding out if a list of Objects contains something with a specified field value?

Question

I have a list of DTO received from a DB, and they have an ID. I want to ensure that my list contains an object with a specified ID. Apparently creating an object with expect

Answer 1

   public boolean containsId(List list, long id) {
    boolean flag = false;
    for (HasId object : list) {
        if (object.getId() == id) {
           flag = true;
        }
    }
    return flag;
}