I prepared the following code to help understand the problem:

0    public class Matrix {
1       public double[][] matrix = new double[10][10];
2       public int size = 10;
3       public void foo(int i, double s) {
4          double[] row = matrix[i];
5          for (int j = 0; j < size; j++) {
6             row[j] += s;
7          }
8       }
9    }

In that code in line 4 I get two hints:
1) The array is only written to and never read from (Which is annoying but technically correct)
2) The assigned value is never used (which is wrong)

The example may seem odd (but it's the best SSCCE I was able to write), this hint is appearing in different (wrong) places, but always with a similar pattern.

Regards

Product Version = NetBeans IDE 8.0 (Build 201403101706)
Operating System = Linux version 3.13.0-24-generic running on amd64
Java; VM; Vendor = 1.7.0_55
Runtime = OpenJDK 64-Bit Server VM 24.51-b03