Flatten Multidimensional String Array of Unknown Size to Single Dimension String Array - Kotlin

StringArrayFlattenExample.kt

package stringarrayflattenexample

/**
 * @author Jesse Jones
 */
class StringArrayFlattenExample {
    fun main(args:Array<String>) {
        //Setup demo data
        val inputArray = arrayOf<Any>(arrayOf<Any>("One", "Two", arrayOf<Any>("Three")), arrayOf<Any>("Four", arrayOf<Any>("Five", arrayOf<Any>("Six")), "Seven"))
        //Flatten Array
        val flatStringArray = flattenStringArray(inputArray)
        //Print flat array to console
        flatStringArray?.let {
            printResults(it)
        }
    }
    
    /**
     * Flatten Multidimensional String Array.
     *
     * @param array - Array you want to flatten
     * @return flattened String array;
     */
    fun flattenStringArray(array:Array<Any>): Array<Any>? {
        val stringArray = ArrayList<Any>()

        //Loop through first level of array
        for (value in array)
        {
            //Search for children within the array
            val childResult = searchChildren(value, stringArray)
            if (childResult != null)
            {
                stringArray.add(childResult)
            }
        }
        return stringArray.toArray()
    }
    
    /**
     * Search parent for sub children
     *
     * @param `object` - the next item in list to search;
     * @param list - the arraylist where results are stored;
     * @return string of child item
     */
    private fun searchChildren(theObject:Any, list:ArrayList<Any>): String? {
        if (theObject is String)
        {
            //If child is a String and not an array, return string
            list.add(theObject)
            return theObject
        }
        else
        {
            //If child is not a String, loop through child array
            val children = theObject as Array<*>
            for (child in children)
            {
                //If not null
                child?.let {
                    //Continue searching for children in more dimensions
                    searchChildren(it, list)
                }
            }
            return null
        }
    }
    
    /**
     * Print the results of our flattened array to console.
     *
     * @param list - the flattened string array to print
     */
    private fun printResults(list: Array<Any>) {
        for (string in list)
        {
            println(string)
        }
    }
}


//Junit5.6 Test Class
import org.junit.Assert.assertArrayEquals
import org.junit.jupiter.api.BeforeEach
import org.junit.jupiter.api.DisplayName
import org.junit.jupiter.api.Test
import stringarrayflattenexample.StringArrayFlattenExample

/**
 *
 * @author Jesse Jones
 */
class StringArrayFlattenTest {

    lateinit var arrayFlattenExample : StringArrayFlattenExample;

    @BeforeEach
    fun setUp() {
        arrayFlattenExample = StringArrayFlattenExample()
    }

    @Test
    @DisplayName("Check Proper String Array Flattening")
    fun testStringArrayFlatten() {
        //Test input data
        val provided = arrayOf<Any>(arrayOf<Any>("One", "Two", arrayOf<Any>("Three")), arrayOf<Any>("Four", arrayOf<Any>("Five", arrayOf<Any>("Six")), "Seven"))
        //Expected test result data
        val expected = arrayOf<Any>("One", "Two", "Three", "Four", "Five", "Six", "Seven")
        assertArrayEquals(expected, arrayFlattenExample.flattenStringArray(provided))
    }
}