/** {@inheritDoc} */
  public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
    // VERSION
    in.readByte();

    // SUPER
    super.readExternal(in);

    // NO_ENTRY_KEY
    no_entry_key = in.readFloat();

    // NO_ENTRY_VALUE
    no_entry_value = in.readDouble();
  }
  /** {@inheritDoc} */
  public void writeExternal(ObjectOutput out) throws IOException {
    // VERSION
    out.writeByte(0);

    // SUPER
    super.writeExternal(out);

    // NO_ENTRY_KEY
    out.writeFloat(no_entry_key);

    // NO_ENTRY_VALUE
    out.writeDouble(no_entry_value);
  }
 /**
  * Releases the element currently stored at <tt>index</tt>.
  *
  * @param index an <code>int</code> value
  */
 @Override
 protected void removeAt(int index) {
   _set[index] = no_entry_key;
   super.removeAt(index);
 }