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

StringArrayFlattenExample.java

package stringarrayflattenexample;

import java.util.ArrayList;
import java.util.List;

/**
 * @author Jesse Jones
 */
public class StringArrayFlattenExample {

    public static void main(String[] args) {
        //Setup demo data
        Object[] inputArray = new Object[]{
            new Object[]{"One", "Two", new Object[]{"Three"}},
            new Object[]{"Four", new Object[]{"Five", new Object[]{"Six"}}, "Seven"}
        };

        //Flatten Array
        Object[] flatStringArray = flattenStringArray(inputArray);

        //Print flat array to console
        printResults(flatStringArray);
    }

    /**
     * Flatten Multidimensional String Array.
     *
     * @param array - Array you want to flatten
     * @return flattened String array;
     */
    public static Object[] flattenStringArray(Object[] array) {
        List<String> stringArray = new ArrayList<String>();

        if (array == null) {
            System.out.println("Array Was Null");
            return null;
        }

        //Loop through first level of array
        for (Object value : array) {
            //Search for children within the array
            Object childResult = searchChildren(value, stringArray);
            if (childResult != null) {
                stringArray.add((String) childResult);
            }
        }

        return stringArray.toArray();
    }

    /**
     * Search parent for sub children
     *
     * @param object - the next item in list to search;
     * @param list - the list where results are stored;
     * @return string of child item
     */
    private static String searchChildren(Object object, List list) {
        if (object instanceof String) {
            //If child is a String and not an array, return string
            list.add((String) object);
            return (String) object;
        } else {
            //If child is not a String, loop through child array
            Object[] children = (Object[]) object;
            for (Object child : children) {
                //Continue searching for children in more dimensions
                searchChildren(child, list);
            }
            return null;
        }
    }

    /**
     * Print the results of our flattened array to console.
     *
     * @param list - the flattened string array to print
     */
    public static void printResults(Object[] list) {
        if (list != null) {
            for (Object string : list) {
                System.out.println(string);
            }
        }
    }

}



//Junit5.6 Test Class
import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.DisplayName;
import org.junit.jupiter.api.Test;
import stringarrayflattenexample.StringArrayFlattenExample;

/**
 *
 * @author Jesse Jones
 */
public class StringArrayFlattenTest {
    
    private StringArrayFlattenExample arrayFlattenExample;
    
    @BeforeEach
    public void setUp(){
        arrayFlattenExample = new StringArrayFlattenExample();
    }
    
    @Test
    @DisplayName("Check Proper String Array Flattening")
    public void testStringArrayFlatten(){
        
        //Test input data
        Object[] provided = new Object[]{
            new Object[]{"One", "Two", new Object[]{"Three"}},
            new Object[]{"Four", new Object[]{"Five", new Object[]{"Six"}}, "Seven"}
        };
        //Expected test result data
        Object[] expected = {"One","Two","Three","Four","Five","Six","Seven"};
        
        assertArrayEquals(expected, arrayFlattenExample.flattenStringArray(provided));
    }
}