Program.java

import org.junit.Test;

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

import static org.junit.Assert.assertTrue;

public class Program {

    private static int memoryVertical = 0;
    private static int memoryHorizontal = 0;
    public static List<Integer> spiralTraverse(int[][] array)
    {
        memoryVertical = array.length;
        memoryHorizontal = array[0].length;

        List<Integer> output = new ArrayList<>();

        goRight(array, output,0, 0, --memoryHorizontal);

        return output;
    }

    private static void goRight(int[][] array, List<Integer> output, int row, int start, int end)
    {
        if(start > end) {
            return;
        }

        for(int i=start; i<=end; i++)
        {
            output.add(array[row][i]);
        }
        goDown(array, output, end, row+1,--memoryVertical);
    }

    private static void goDown(int[][] array, List<Integer> output, int column, int start, int end)
    {
        if(start > end) {
            return;
        }

        for(int i=start; i<=end; i++)
        {
            output.add(array[i][column]);
        }
        goLeft(array, output, end, column-1, array[0].length - memoryHorizontal -1);
    }

    private static void goLeft(int[][] array, List<Integer> output, int row, int start, int end)
    {
        if(start < end) {
            return;
        }

        for(int i=start; i>=end; i--)
        {
            output.add(array[row][i]);
        }

        goUp(array, output, end, row-1,array.length - memoryVertical);
    }

    private static void goUp(int[][] array, List<Integer> output, int column, int start, int end)
    {
        if(start < end) {
            return;
        }

        for(int i=start; i>=end; i--)
        {
            output.add(array[i][column]);
        }
        goRight(array, output, end, column+1,--memoryHorizontal);
    }

}