如何在 Java8 单行中将字符串数组转换为长数组？

Question

I'm solving the "Count Triplets" problem on HackerRank. https://www.hackerrank.com/challenges/count-triplets-1/problem?h_l=interview&playlist_slugs%5B%5D=interview-preparation-kit&playlist_slugs%5B%5D=dictionaries-hashmaps It says that I must work with an array, although HC converts it to a List. I want to convert in into an array instead of a list.

public static void main(String[] args) throws IOException {
        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH")));

        String[] nr = bufferedReader.readLine().replaceAll("\\s+$", "").split(" ");

        int n = Integer.parseInt(nr[0]);

        long r = Long.parseLong(nr[1]);

        **List<Long> arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                .map(Long::parseLong)
                .collect(toList());**

        long ans = countTriplets(arr, r);

        bufferedWriter.write(String.valueOf(ans));
        bufferedWriter.newLine();

        bufferedReader.close();
        bufferedWriter.close();
    }

Answer 1

Do it as follows:

Long[] arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                .map(Long::parseLong)
                .collect(Collectors.toList())
                .toArray(Long[]::new);

Update:

Courtesy Holger

There is no need to collect into a List as shown above. You can do it simply as

Long[] arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                .map(Long::parseLong)
                .toArray(Long[]::new);

Alternatively,

long[] arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                .mapToLong(Long::parseLong) 
                .toArray()

Answer 2

Use .toArray(Long[]::new) instead of .collect(Collectors.toList())

Long[] arr = Stream.of(bufferedReader.readLine().replaceAll("\\s+$", "").split(" "))
                   .map(Long::parseLong)
                   .toArray(Long[]::new);