Design for collections upgrades

Rémi Forax forax at
Mon Mar 14 07:20:28 PDT 2011

On 03/14/2011 02:30 PM, Craig P. Motlin wrote:
> There are two forms of lazy evaluation and I see people using the same term
> (Stream) to refer to both. In Scala they are called view and stream and I
> was confused about the difference so I asked on Stack Overflow. Basically
> the difference is:
> In a view elements are recomputed each time they are accessed. In a stream
> elements are retained as they are evaluated.
> I think that Java collections ought to support both, which is another reason
> I think that eager ought to be the default. See the full explanation here:

But memoization is hard to provide when your original collection is mutable:

What does this code print ?

LinkedList<Integer> list = new LinkedList<>();
Collections.addAll(list, 1, 2, 3, 4, 5);
List<Integer> list2 = list.asScalaStreamPlease();
System.out.println(list2.join(" "));   // the whole list is now memoized

list.remove(0); // wink wink
System.out.println(list2.join(" "));


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