number format exception when extracting an integer from SQLITE database table

Question

I've looked at similar questions but non had the same issue I'm having. My application keeps crashing on addQuestion() method and for the life of me I couldn't pin point down the problem. The error log shows number format exception at line 176 int difficulty = Integer.parseInt(cursor.getString(2)); I reviewed my code very carefully for possible SQL syntax errors but couldn't find anything. Here's my addQuestion method

public void addQuestion(Question question, String question_type){

   SQLiteDatabase db = getWritableDatabase();

    String query = "SELECT body FROM questions where body = '" +question.getBody()+"'";
    Cursor cr = db.rawQuery(query, null);

    if(cr.getCount() > 0){
        db.close();
        return;
    }
    else {
        ContentValues cv = new ContentValues();
        cv.put(type, question_type);
        cv.put(body, question.getBody());
        cv.put(answer, question.getAnswer());
        cv.put(difficulty, question.getDifficulty());

        try {
            db.insert(questions_table, null, cv);
        } catch (SQLiteException e) {
            e.getMessage();
        }
    }
    db.close();
}

and here's my getQuestion by type method:

public Question getQuestionByType(String type){
    SQLiteDatabase db = getWritableDatabase();
    String query = "SELECT " + body + "," + answer + "," + difficulty + " FROM " + questions_table + " WHERE "
          +  this.type + " ='" + type+"';";

    Cursor cursor = db.rawQuery(query, null);
    cursor.moveToFirst();
    String body = cursor.getString(0);
    String answer = cursor.getString(1);
    int difficulty = Integer.parseInt(cursor.getString(2));
    db.close();

    return new Question(type, body, answer, difficulty);
}

Here's the log output

   java.lang.NumberFormatException: null
                                                                  at java.lang.Integer.parseInt(Integer.java:483)
                                                                  at java.lang.Integer.parseInt(Integer.java:556)
                                                                  at com.maz.quizzdat.DbHandler.getQuestionByType(DbHandler.java:176)
                                                                  at com.maz.quizzdat.MainActivity$1.onClick(MainActivity.java:47)

Any help is appreciated.

Edit: for those of you who may run into a similar situation, you cannot use Integer.parseInt(); in this particular situation on a string, even though the string is in fact a number. Use curser.getInt() instead of Integer.parseInt(curser.getString())

As your log show it may be the `difficulty` in your db are null — TuyenNTA, May 14 '17 at 22:35
It says the data in that column is `null`. Are you sure your query matches any data in the third column? Are `body` and `answer` non-null? — River, May 14 '17 at 22:35
Possible duplicate of [What is a NumberFormatException and how can I fix it?](http://stackoverflow.com/questions/39849984/what-is-a-numberformatexception-and-how-can-i-fix-it) — Jason, May 14 '17 at 22:36
Yes. The right way to do it was to use curser.getInt(2); since, clever me, i'm getting an int not a string. — MZ4Code, May 14 '17 at 22:38
Just a tip going forward, your code is vulnerable to SQL injection attacks. Please investigate using prepared statements and you'll be better for it. — Jason, May 14 '17 at 22:39
Thanks @Jason. This is my first app using SQL (First app in general) I will definitely look into it once the basic functionalities are done. — MZ4Code, May 14 '17 at 23:50

score 2 · Accepted Answer · answered May 14 '17 at 22:33

2

Try cursor.getInt(2) instead of getString(2), since that column contains Integers?

https://developer.android.com/reference/android/database/Cursor.html#getInt(int)

Edit: parseInt() obviously is not necessary anymore then.

answered May 14 '17 at 22:33

enigma969

397
6
21

Author added log output after I made my answer! – enigma969 May 14 '17 at 22:36
@MZ4Code ah, I figured the method just read the integer as a String, but oddly it just returns null if its not a string-type – River May 14 '17 at 22:40
@River yea me too. I'll play around with it and see why I was getting such a "strange" error. So the question is. Had I had my difficulty column to be char rather that int, would I have been able to user Integer.parseInt()? – MZ4Code May 14 '17 at 22:40
@River no, I still got the same numberformat error after trying to parse the result to an int – MZ4Code May 14 '17 at 22:42
1

@MZ4Code the answer is [here](https://developer.android.com/reference/android/database/Cursor.html#getString(int)). *The result and whether this method throws an exception when the column type is __not a string type__ is implementation-defined.* – River May 14 '17 at 22:42

score 0 · Answer 2 · edited May 15 '17 at 01:23

0

You should use if(cursor .getCount() > 0) before cursor.moveToFirst() in your getQuestionByType method to be sure that the query has a result, then you can use cursor.getInt(0)

edited May 15 '17 at 01:23

River

8,585
14
54
67

answered May 14 '17 at 22:41

Ben ElFekih

19
4

This is only a check to make sure the question does not already exist in the table. – MZ4Code May 14 '17 at 22:42
This should be a comment about good practices, it doesn't answer the question. – River May 14 '17 at 22:42
See his reputation? He's not yet able to comment – esQmo_ May 14 '17 at 22:44

number format exception when extracting an integer from SQLITE database table

2 Answers2