@Override
 public int hashCode() {
   final int prime = 31;
   int result = 1;
   result = prime * result + ((carrera == null) ? 0 : carrera.hashCode());
   result = prime * result + ((id == null) ? 0 : id.hashCode());
   result = prime * result + ((persona == null) ? 0 : persona.hashCode());
   return result;
 }
 @Override
 public boolean equals(Object obj) {
   if (this == obj) return true;
   if (obj == null) return false;
   if (getClass() != obj.getClass()) return false;
   CarreraEstudiante other = (CarreraEstudiante) obj;
   if (carrera == null) {
     if (other.carrera != null) return false;
   } else if (!carrera.equals(other.carrera)) return false;
   if (id == null) {
     if (other.id != null) return false;
   } else if (!id.equals(other.id)) return false;
   if (persona == null) {
     if (other.persona != null) return false;
   } else if (!persona.equals(other.persona)) return false;
   return true;
 }