public void shiftRow (int offset)
{
	// say there's an array called arr.
	int [][] newArr = new int[arr.length][arr[0].length];
	if (offset >= arr.length)
		return;
	for (int i = 0; i < newArr.length; i++)
	{
		for (int j = 0; j < newArr.length; j++)
		{
			if (offset > i)
				newArr[i][j] = 0;
			else if (offset < 0 && i - offset > newArr.length)
				newArr[i][j] = 0;
			else //default case.
				newArr[i][j] = arr[i - offset][j];
		}
	}
}