code: private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
      s.defaultWriteObject();
  
      // Write out array length
      int length = length();
      s.writeInt(length);
  
      // Write out all elements in the proper order.
      for (int i = 0; i < length; i++) {
        s.writeDouble(get(i));
      }
    }
docs: Saves the state to a stream (that is, serializes it).
  
  @serialData The length of the array is emitted (int), followed by all of its elements (each a
  {@code double}) in the proper order.