Coding Challenge: Java Fundamentals

✒ Reference: Create Phone Number

Some simple challenges to brush up on Java!

Challenge 1 - Regex

Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.

// Example:
Kata.createPhoneNumber(new int[] {1, 2, 3, 4, 5, 6, 7, 8, 9, 0}) 
// => returns "(123) 456-7890"

My solution:

public class Kata {
  public static String createPhoneNumber(int[] numbers) {
    return String.format("(%d%d%d) %d%d%d-%d%d%d%d",numbers[0],numbers[1],numbers[2],numbers[3],numbers[4],numbers[5],numbers[6],numbers[7],numbers[8],numbers[9]);
  }
}

Best solution suggested to spice up the regex as below:

String.format("(%d%d%d) %d%d%d-%d%d%d%d", java.util.stream.IntStream.of(numbers).boxed().toArray());

• java.util.stream package supports functional-style operations on streams of elements, such as map-reduce transformations on collections.
• The stream(T[] array) method returns a sequential Stream with the elements of the array, passed as parameter, as its source.
• IntStream returns a sequence of primitive int-valued elements.