Transform values with a stream

The goal is to transform an array of numbers into a comma-delimited string using functional programming. The code snippet you provided has a minor issue: String.join(",", strings[0]) is incorrect because it tries to join a single element (strings[0]) rather than all elements in the strings array.

Here's the corrected code for the transformValues method:

import java.util.Arrays;


class Answer {


    // Change these boolean values to control whether you see 

    // the expected answer and/or hints.

    static boolean showExpectedResult = true;

    static boolean showHints = true;


    // Transform an array of numbers into a comma-delimited list

    // using functional programming.

    static String transformValues(int[] numbers) {

        // Convert the int array to a stream of integers

        // Map each integer to its String representation

        // Collect the results into a String array

        String[] strings = Arrays.stream(numbers)

                                  .mapToObj(String::valueOf)

                                  .toArray(String[]::new);

        // Join the array of strings into a single comma-delimited string

        return String.join(",", strings);

    }


    public static void main(String[] args) {

        int[] numbers = {1, 2, 3, 4, 5};

        String result = transformValues(numbers);

        System.out.println(result);  // Output: 1,2,3,4,5

    }

}

Explanation

  1. Convert Array to Stream: Arrays.stream(numbers)  Converts the int[] array to an IntStream.

  2. Map to String: mapToObj(String::valueOf) Maps each int in the stream to its String representation using String::valueOf.

  3. Collect to Array: .toArray(String[]::new) Collects the results into a String[] array.

  4. Join Strings: String.join(",", strings) Joins all elements of the String[] array into a single String, with each element separated by a comma.

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