code: public int size()
      {
          class CountProcedure implements Procedure<C>
          {
              private static final long serialVersionUID = 1L;
  
              private int totalSize;
  
              public void value(C collection)
              {
                  this.totalSize += collection.size();
              }
  
              public int getTotalSize()
              {
                  return this.totalSize;
              }
          }
  
          CountProcedure procedure = new CountProcedure();
          this.map.forEachValue(procedure);
          return procedure.getTotalSize();
      }
docs: Query Operations