### Question:
MatrixUtils { public static double[][] accessMatrixDataDirectly(RealMatrix matrix) { try { return (double[][]) MATRIX_DATA_FIELD.get(matrix); } catch (IllegalAccessException iae) { throw new IllegalStateException(iae); } } private  MatrixUtils(); static void addTo(long row,
                           long column,
                           float value,
                           LongObjectMap<LongFloatMap> RbyRow,
                           LongObjectMap<LongFloatMap> RbyColumn); static void remove(long row,
                            long column,
                            LongObjectMap<LongFloatMap> RbyRow,
                            LongObjectMap<LongFloatMap> RbyColumn); static boolean isNonSingular(RealMatrix M); static Solver getSolver(RealMatrix M); static double[][] accessMatrixDataDirectly(RealMatrix matrix); static RealMatrix transposeTimesSelf(LongObjectMap<float[]> M);  }### Answer:
@Test public void testAccess() { double[][] data = { new double[] {1}, }; RealMatrix matrix = new Array2DRowRealMatrix(data, false); assertSame(data, MatrixUtils.accessMatrixDataDirectly(matrix)); }