public static DoubleStream concat(DoubleStream a,DoubleStream b){
  Objects.requireNonNull(a);
  Objects.requireNonNull(b);
  Spliterator.OfDouble split=new Streams.ConcatSpliterator.OfDouble(a.spliterator(),b.spliterator());
  DoubleStream stream=StreamSupport.doubleStream(split,a.isParallel() || b.isParallel());
  return stream.onClose(Streams.composedClose(a,b));
}

public static DoubleStream concat ( DoubleStream a , DoubleStream b ) { Objects . requireNonNull ( a ) ; Objects . requireNonNull ( b ) ; Spliterator . OfDouble split = new Streams . ConcatSpliterator . OfDouble ( a . spliterator ( ) , b . spliterator ( ) ) ; DoubleStream stream = StreamSupport . doubleStream ( split , a . isParallel ( ) || b . isParallel ( ) ) ; return stream . onClose ( Streams . composedClose ( a , b ) ) ; }
creates a lazily concatenated stream whose elements are all the elements of the first stream followed by all the elements of the second stream . the resulting stream is ordered if both of the input streams are ordered , and parallel if either of the input streams is parallel . when the resulting stream is closed , the close handlers for both input streams are invoked .
