code: public static Stream<Double> box(final double[] doubles) {
          return new FixedSizeStream<>(doubles.length, new Func1<Integer, Double>() {
              @Override
              public Double call(Integer index) {
                  return doubles[index];
              }
          });
      }
docs: Creates a new stream of {@link Double} type that contains all items of a given array.
  
  @param doubles an array to get items from.
  @return a new stream of {@link Double} type that contains all items of a given array.