“java.lang.NullPointerException: Attempt to write to null array” for int[][] var = new int[m][n]

Question

I'm getting this weird exception report from other users:

java.lang.NullPointerException: Attempt to write to null array
    at yuku.alkitab.base.util.Levenshtein.distance(Levenshtein.java:16)

The relevant snippet is:

private static final int deletion = 500;

public static int distance(String s, String t) {
    // d is a table with m+1 rows and n+1 columns
    int m = s.length();
    int n = t.length();

    int[][] d = new int[m + 1][n + 1];

    for (int i = 0; i <= m; i++) {
        d[i][0] = i * deletion; // <------ this is line 16
    }

    // more lines omitted
}

Examining the above code I could not find out how that exception can ever happened. Did I miss something?

All crash reports came from Android 6.0, API 23.

Answer 1

Please provide more information to the question. Currently the only thing that should make the code not work, is that it is not returning the value it should return (int).