code: public JsonSet withIdStrategy(IdStrategy strategy) {
          this.strategy = strategy;
          if(size()>0) {
              JsonSet seen=new JsonSet().withIdStrategy(strategy);
              Iterator<JsonElement> iterator = this.iterator();
              while (iterator.hasNext()) {
                  JsonElement e = iterator.next();
                  if(seen.contains(e)) {
                      iterator.remove();
                  } else {
                      seen.add(e);
                  }
              }
          }
          return this;
      }
docs: Changes the strategy on the current set.
  @param strategy id strategy
  @return the current set.