Saving a grid of binary values.

Example code from http://stackoverflow.com/questions/9349519/how-to-convert-boolean-array-to-binary-and-vice-versa-in-java

private static void writeBooleans(OutputStream out, boolean[] ar) throws IOException
{
    for (int i = 0; i < ar.length; i += 8)
    {
        int b = 0;
        for (int j = Math.min(i + 7, ar.length-1); j >= i; j--)
        {
            b = (b << 1) | (ar[j] ? 1 : 0);
        }
        out.write(b);
    }
}

private static void readBooleans(InputStream in, boolean[] ar) throws IOException
{
    for (int i = 0; i < ar.length; i += 8)
    {
        int b = in.read();
        if (b < 0) throw new EOFException();
        for (int j = i; j < i + 8 && j < ar.length; j++)
        {
            ar[j] = (b & 1) != 0;
            b >>>= 1;
        }
    }
}

My code, with variable names changed for clarity and consistency with the above example:

Grid is a square of GridSize height and width.

For writing:

for(int y = 0; y < gridSize; y++)
{
    for(int i = 0; i < gridSize; i += 8)
    {
        int b = 0;

        for(int j = Math.min(i + 7, gridSize - 1); j >= i; j--)
            b = (b << 1) | (grid.get(i, y) ? 1 : 0); // if grid were a boolean[][], grid.get(i, y) would be grid[i][y]

        output.write(b);
    }
}

For reading:

for(int y = 0; y < gridSize; y++)
{
    for(int i = 0; i < gridSize; i += 8)
    {
        int b = input.read();

        if(b < 0)
            throw new EOFException();

        for(int j = i; j < i + 8 && j < gridSize; j++)
        {
            grid.set(j, y, (b & 1) != 0); // Or, if grid were a boolean[][], grid[j][y] = (b & 1) != 0;
            b >>>= 1;
        }
    }
}


My code, with actual variable names:

For writing:

for(int y = 0; y < regionSize; y++)
{
    for(int x = 0; x < regionSize; x += 8)
    {
        int b = 0;

        for(int i = Math.min(x + 7, regionSize - 1); i >= x; i--)
            b = (b << 1) | (region.get(x, y) ? 1 : 0);

        output.write(b);
    }
}

For reading:

for(int y = 0; y < regionSize; y++)
{
    for(int x = 0; x < regionSize; x += 8)
    {
        int b = input.read();

        if(b < 0)
            throw new EOFException();

        for(int i = x; i < x + 8 && i < regionSize; i++)
        {
            region.set(i, y, (b & 1) != 0);
            b >>>= 1;
        }
    }
}