code: public void setDefaultValueStrategy(final DefaultValueStrategy defaultValueStrategy) {
          if (entities.size() > 0) {
              throw new IllegalStateException("The default value strategy cannot be changed after an entity was generated!");
          }
          if (defaultValueStrategy == null) {
              this.defaultValueStrategy = new DefaultDefaultValueStrategy();
          } else {
              this.defaultValueStrategy = defaultValueStrategy;
          }
      }
docs: Sets the default value strategy. May only be called before entities are created, otherwise an {@link IllegalStateException} gets thrown.
  Passing {@code null} resets the strategy to a {@link DefaultDefaultValueStrategy}.
  
  @param defaultValueStrategy The new default value strategy to use from now on