Spiral

    static int sizeOfSide = 5;
//    static int sizeOfArray = sizeOfSide - 1;
    static int[][] matrix = new int[sizeOfSide][sizeOfSide];
    static int count = 1;
    public static void main(String[] args) {
        int level = 0;
        for (level = 0; level < sizeOfSide / 2; level++) {
            fillFourSides(level);
        }
        // Filling last element
        if (sizeOfSide % 2 == 1) {
            matrix[level][level] = count++;
        }
        printMatrix(matrix, 4);
    }


    private static void fillFourSides(int level) {
        // Filling top side
        for (int i = 0 + level; i < sizeOfSide - level; i++) {
            matrix[level][i] = count++;
        }
        // Filling right side
        for (int i = 1 + level; i < sizeOfSide - level; i++) {
            matrix[i][sizeOfSide - 1 - level] = count++;
        }
        // Filling bottom
        for (int i = sizeOfSide - 2 - level; i >= level; i--) {
            matrix[sizeOfSide - 1 - level][i] = count++;
        }
        // Filling left side
        for (int i = sizeOfSide - 2 - level; i >= level + 1 ; i--) {
            matrix[i][level] = count++;
        }
    }

    private static void printMatrix(int[][] matrix, int digits) {
        String pattern = "%" + digits + "d";
        for (int i = 0; i < sizeOfSide; i++) {
            for (int j = 0; j < sizeOfSide; j++) {
                System.out.printf(pattern, matrix[i][j]);
            }
            System.out.println();
        }
    }