code: public void readFields(DataInput in) throws IOException {
      
      // Get the number of "unknown" classes
      
      newClasses = in.readByte();
      
      // Then read in the class names and add them to our tables
      
      for (int i = 0; i < newClasses; i++) {
        byte id = in.readByte();
        String className = in.readUTF();
        try {
          addToMap(Class.forName(className), id);
          
        } catch (ClassNotFoundException e) {
          throw new IOException("can't find class: " + className + " because "+
              e.getMessage());
        }
      }
    }
docs: {@inheritDoc}