DiagonalMatrix extends AbstractRealMatrix implements Serializable { @Override public void addToEntry(final int row, final int column, final double increment) throws OutOfRangeException, NumberIsTooLargeException { if (row == column) { MatrixUtils.checkRowIndex(this, row); data[row] += increment; } else { ensureZero(increment); } } DiagonalMatrix(final int dimension);  DiagonalMatrix(final double[] d);  DiagonalMatrix(final double[] d, final boolean copyArray); @Override RealMatrix createMatrix(final int rowDimension,
                                   final int columnDimension); @Override RealMatrix copy(); DiagonalMatrix add(final DiagonalMatrix m); DiagonalMatrix subtract(final DiagonalMatrix m); DiagonalMatrix multiply(final DiagonalMatrix m); @Override RealMatrix multiply(final RealMatrix m); @Override double[][] getData(); double[] getDataRef(); @Override double getEntry(final int row, final int column); @Override void setEntry(final int row, final int column, final double value); @Override void addToEntry(final int row,
                           final int column,
                           final double increment); @Override void multiplyEntry(final int row,
                              final int column,
                              final double factor); @Override int getRowDimension(); @Override int getColumnDimension(); @Override double[] operate(final double[] v); @Override double[] preMultiply(final double[] v); @Override RealVector preMultiply(final RealVector v); DiagonalMatrix inverse(); DiagonalMatrix inverse(double threshold); boolean isSingular(double threshold);  }
@Test public void testAddToEntry() { final double[] data = { -1.2, 3.4, 5 }; final DiagonalMatrix m = new DiagonalMatrix(data); for (int i = 0; i < m.getRowDimension(); i++) { m.addToEntry(i, i, i); Assert.assertEquals(data[i] + i, m.getEntry(i, i), 0d); } }
@Test(expected=NumberIsTooLargeException.class) public void testAddNonDiagonalEntry() { final DiagonalMatrix diag = new DiagonalMatrix(3); diag.addToEntry(1, 2, 3.4); }