private static void removeRegion(int[][] a, int i, int j) {
        if (i < 0 || j < 0 || i >= a.length || j >= a.length)
            return;
        if (a[i][j] == 0)
            return;
        a[i][j] = 0;
        removeRegion(a, i + 1, j);
        removeRegion(a, i - 1, j);
        removeRegion(a, i, j + 1);
        removeRegion(a, i, j - 1);
    }
Why Did you create this class? what does it do?
src/adventofcode/DiskDefragmentation_14.java