code: public float getBoxUsage() {
          String boxUsage = metadata.get(BOX_USAGE);
          if (boxUsage == null || boxUsage.trim().length() == 0)
              return 0;
          return Float.parseFloat(boxUsage);
      }
docs: Returns the SimpleDB box usage reported in a response's metadata. SimpleDB box usage
  indicates how much compute capacity was used to process your request.
  <p>
  Box usage is useful when looking at how different queries perform on your data. You can use
  that information to tune your queries, and reduce your monthly SimpleDB usage charges.
  
  @return The SimpleDB box usage reported for the associated request.