Fill the number in 2d array circulating in a spiral.

Square.java

package com.sangmoon.square;

public class Square {

    public static void main(String arg[]){
        int N = Integer.parseInt(arg[0]);
        int[][] map = new int[N][N];

        Square s = new Square();

        s.solve(0, 0, map, 1, N);

        for (int i=0; i< N; i++){
            for (int j =0; j<N; j++){
                System.out.format("%02d  ", map[i][j]);
            }
            System.out.println();
        }
    }

    public void solve(int startX, int startY, int[][] map, int k, int n){

        int posX = startX;
        int posY = startY;
        int idx = 1;
        
        map[posX][posY] = k;
        if (n == 1)
            return;
            
        idx++;
        k++;

        Direction d = Direction.RIGHT;

        Counter c = new Counter(n-1);
        

        while(idx <= 4*n -4){
            posX += d.getX();
            posY += d.getY();

            map[posX][posY] = k;
            idx++;
            k++;

            c.count();
            if (c.getCount() == n - 1){
                switch (d){
                    case RIGHT:
                        d = Direction.DOWN;
                        break;
                    case DOWN:
                        d = Direction.LEFT;
                        break;
                    case LEFT:
                        d = Direction.UP;
                        break;
                    default:
                        System.out.println("nonono");
                }
            }
        }

        if ( n == 2 ){
            return;
        } else {
            solve(posX, posY +1, map, k, n -2  );
        }


    }
}

enum Direction {
    RIGHT(0, 1), LEFT(0, -1), DOWN(1, 0), UP(-1, 0);

    public int getX() {
        return x;
    }

    public int getY() {
        return y;
    }

    private int x;
    private int y;

    Direction(int x, int y){
        this.x = x;
        this.y = y;
    }
}

class Counter{
    private int initCount;
    private int count;

    Counter(int n){
        initCount = n;
        count = n;
    }

    public void count(){
        count --;
        if (count == 0)
            count = initCount;
        return;
    }

    public int getCount(){
        return count;
    }
}