code: public Entity getWeak(Field field) {
          for (Entity entity : getWeaks()) {
              if (entity.getOwner().getEntityProperty().equals(field.getProperty())) {
                  return entity;
              }
          }
          return null;
      }
docs: Looks for the weak entity corresponding to the given field in this string
  entity
  
  @param field
  @return the weak entity