@GwtIncompatible("java.io.ObjectOutputStream")
  private void writeObject(ObjectOutputStream stream) throws IOException {
    stream.defaultWriteObject();
    stream.writeObject(keyType);
    stream.writeObject(valueType);
    Serialization.writeMap(this, stream);
  }
@ GwtIncompatible ( "java.io.ObjectOutputStream" ) private void writeObject ( ObjectOutputStream stream ) throws IOException { stream . defaultWriteObject ( ) ; stream . writeObject ( keyType ) ; stream . writeObject ( valueType ) ; Serialization . writeMap ( this , stream ) ; }
@serialData the key class, value class, number of entries, first key, first
value, second key, second value, and so on.