MATH-1425: Overridden methods for improved performance.

Thanks to Christoph Dibak.

src/main/java/org/apache/commons/math4/linear/Array2DRowRealMatrix.java

@@ -562,4 +562,28 @@ public class Array2DRowRealMatrix extends AbstractRealMatrix implements Serializ
         throws DimensionMismatchException, NoDataException, NullArgumentException {
         setSubMatrix(in, 0, 0);
     }
+
+    /** {@inheritDoc} */
+    @Override
+    public double[] getRow(final int row)
+        throws OutOfRangeException {
+        MatrixUtils.checkRowIndex(this, row);
+        final int nCols = getColumnDimension();
+        final double[] out = new double[nCols];
+        System.arraycopy(data[row], 0, out, 0, nCols);
+        return out;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public void setRow(final int row,
+                       final double[] array)
+        throws OutOfRangeException, MatrixDimensionMismatchException {
+        MatrixUtils.checkRowIndex(this, row);
+        final int nCols = getColumnDimension();
+        if (array.length != nCols) {
+                throw new MatrixDimensionMismatchException(1, array.length, 1, nCols);
+        }
+        System.arraycopy(array, 0, data[row], 0, nCols);
+    }
 }