Review

class BooleanQuery.BooleanWeight {
    public Explanation explain(IndexReader reader, int doc)
      throws IOException {
      Explanation sumExpl = new Explanation();
      sumExpl.setDescription("sum of:");
      int coord = 0;
      int maxCoord = 0;
      float sum = 0.0f;
      for (int i = 0 ; i < weights.size(); i++) {
        BooleanClause c = (BooleanClause)clauses.elementAt(i);
        Weight w = (Weight)weights.elementAt(i);
        Explanation e = w.explain(reader, doc);
        if (!c.prohibited) maxCoord++;
        if (e.getValue() > 0) {
          if (!c.prohibited) {
            sumExpl.addDetail(e);
            sum += e.getValue();
            coord++;
          } else {
            return new Explanation(0.0f, "match prohibited");
          }
        } else if (c.required) {
          return new Explanation(0.0f, "match required");
        }
      }
      sumExpl.setValue(sum);

      if (coord == 1)                               // only one clause matched
        sumExpl = sumExpl.getDetails()[0];          // eliminate wrapper

      float coordFactor = getSimilarity(searcher).coord(coord, maxCoord);
      if (coordFactor == 1.0f)                      // coord is no-op
        return sumExpl;                             // eliminate wrapper
      else {
        Explanation result = new Explanation();
        result.setDescription("product of:");
        result.addDetail(sumExpl);
        result.addDetail(new Explanation(coordFactor,
                                         "coord("+coord+"/"+maxCoord+")"));
        result.setValue(sum*coordFactor);
        return result;
      }
    }

}