private void readObject(java.io.ObjectInputStream s) throws IOException, ClassNotFoundException  {
    s.defaultReadObject();      // Read nothing
    final int len = s.readInt(); // Read max element
    _nbsi = new NBSI(len, new ConcurrentAutoTable(), this);
    for( int i=0; i<len; i++ )  // Read all bits
      if( s.readBoolean() )
        _nbsi.add(i);
  }
Standard Java {@link Iterator}.  Not very efficient because it
auto-boxes the returned values.
jctools-core/src/main/java/org/jctools/maps/NonBlockingSetInt.java