List to Map using Lambda expressions

Question

I want to transform a list of String to a map, where the key of map is a simple increment.

For example:

List<String> result = new ArrayList<String>();
result.add("hello");
result.add("Java");

Pretend result:

Map<Integer, String> mapOfList;
map(1, "Hello");
map(2, "Java");

Try:

AtomicInteger atomic=new AtomicInteger(0);
mapOfList=result.stream().collect(atomic.incrementAndGet(), s -> s);

Your question is unclear. Can you elaborate on it? Also, create some examples. And don't confuse arrays with lists. An `ArrayList` has nothing to do with an array, both are completely different structures. — Zabuzard, Aug 06 '18 at 13:21
Your question is unclear. I have no idea what you are asking for. — Zabuzard, Aug 06 '18 at 13:22
You cannot do that without an iteration. Even existing functions that fill an array use iteration internally. — f1sh, Aug 06 '18 at 13:22
What does it mean for an element to be empty? Do you mean null? Empty string? — Brandon, Aug 06 '18 at 13:23
Assuming you understand that this is an `ArrayList` and not an array, you can empty the entire list using `ArrayList.clear()`. Maybe that is what you are trying to do? It's really tough to understand what you are trying to do. Your words are confusing. You are saying both "fill" and "empty" — Brandon, Aug 06 '18 at 13:24
Pulling another thread: you asked how to do this to each element without iteration. When doing something repetitively, the alternative to iteration is recursion. Using recursion to walk sequentially over an array though is strange. — Brandon, Aug 06 '18 at 13:26
@Brandon what I mean was visually. Instead of making something like for(...) — Goldbones, Aug 06 '18 at 13:29

score 2 · Accepted Answer · answered Aug 06 '18 at 13:24

2

You need to iterate. Here's one-line using an int stream:

IntStream.range(0, fillMyList.size()).forEach(i -> fillMyList.set(i, ""));

answered Aug 06 '18 at 13:24

ernest_k

1 Answers1