I want to write a loop that references an index with Java 8's Stream API

Everyone loves Stream API, Loops like writing in an extended for statement are clean, but I don't know what to do with a loop that wants to refer to the index inside the loop. (There is a way to create your own class even if you go around: persevere :)

So I twisted my head a little.

The following cases are assumed as "loops that want to refer to the index inside the loop".

――I want to turn two or more lists together --I also want to refer to adjacent elements in one list (such as ʻi-1 or ʻi + 1 for ʻi`)

(Because you can refer to ʻi` and write your favorite process It can also be used in cases such as "I want to change the process at the beginning / end of the list", I think it's not very beautiful. )

Below is a code example.

    public static void main(String[] args) {
        //Appropriate list made of random numbers
        List<Integer> listA = new ArrayList<>(Arrays.asList(12, 23, 66, 45, 10, 48, 21, 25, 68, 65));
        List<Integer> listB = new ArrayList<>(Arrays.asList(98, 96, 4, 33, 30, 38, 39, 25, 32, 64));

        //Case 1: If you want to handle two lists together
        List<Boolean> isWinnerA = IntStream.range(0, Math.min(listA.size(), listB.size()))
                .mapToObj(i -> listA.get(i) > listB.get(i))
        System.out.println("isWinnerAList: " + isWinnerAList);
        // -> isWinnerA: [false, false, true, true, false, true, false, false, true, true]

        //Case 2: If you want to handle the front and back of the list together
        List<Double> movingAverage = IntStream.range(0, listA.size() - 1)
                .mapToObj(i -> (listA.get(i) + listA.get(i + 1)) / 2d)
        System.out.println("movingAverage: " + movingAverage);
        // -> movingAverage: [17.5, 44.5, 55.5, 27.5, 29.0, 34.5, 23.0, 46.5, 66.5]

As a composition,

--for (int i; i <list.size (); i ++) part --Created with the factory method of ʻIntStream --For a simple increase like the example, you can userange (startInclusive, endExclusive) --If you want to change the magnitude of the increment, you can use ʻiterate (seed, f) .limit (maxSize) (although you can refer to ʻi * 2). --You should be able to do most things with generate (s) --Processing inside the loop --mapToObj (/ * conversion process * /) .collect (/ * aggregate process * /); --If you don't need to aggregate, you can useforEach ()`.

pro: You can write only with the standard ones con: Stream You may be confused if you are not accustomed to it

Is it said that it is better to write in a for sentence normally? Well, if it is the one used in the example, it may be a normal for document, but can it be used in cases such as filter (), aggregation processing, and Stream functions? I think.

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