迭代构建流的最佳方法是什么？

Question

假设我们有一个算法在循环中顺序生成项目(每次迭代一个项目),我们希望将此算法放入一个返回这些项目流的方法中.

哪种方法最好; 这个？

Stream<Cell> streamCellsTouchingRay(Point2D fromPoint, Vector2D direction){
    // ...
    Stream<Cell> stream = Stream.of(/* 1st item */);
    while(/* ... */){
        // ...
        stream = Stream.concat(stream, /* i'th item */);
    }
}

......还是这个？

Stream<Cell> streamCellsTouchingRay(Point2D fromPoint, Vector2D direction){
    // ...
    ArrayList<Cell> cells = new ArrayList<>(/* required capacity is known */);
    cells.add(/* 1st item */);
    while(/* ... */){
        // ...
        cells.add(/* i'th item */);
    }
    return cells.stream();
}

......还是其他方法呢？

Answer 1

完全另一种方法:使用Stream.Builder.

Stream<Cell> streamCellsTouchingRay(Point2D fromPoint, Vector2D direction){
    // ...
    Stream.Builder<Cell> cells = Stream.builder();
    cells.add(/* 1st item */);
    while(/* ... */){
        // ...
        cells.add(/* i'th item */);
    }
    return cells.build();
}