class BlockRealMatrix extends AbstractRealMatrix implements Serializable {

    @Override
    public double getEntry(final int row, final int column)
        throws OutOfRangeException {
        MatrixUtils.checkMatrixIndex(this, row, column);
        final int iBlock = row / BLOCK_SIZE;
        final int jBlock = column / BLOCK_SIZE;
        final int k = (row - iBlock * BLOCK_SIZE) * blockWidth(jBlock) +
            (column - jBlock * BLOCK_SIZE);
        return blocks[iBlock * blockColumns + jBlock][k];
    }

    public  BlockRealMatrix(final int rows, final int columns);
    public  BlockRealMatrix(final double[][] rawData);
    public  BlockRealMatrix(final int rows, final int columns,
                           final double[][] blockData, final boolean copyArray);

}