Check returned value by res is null

Question

this is my code to check if the value of column is not null

if(!res.getString(res.getColumnIndex("answerquestionid")).trim().equals("")){

but I get this:

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String java.lang.String.trim()' on a null object reference

What is the proper way to check if value return by res is empty

looks like res is null in if-statement. please provide some more code — XtremeBaumer, Nov 14 '16 at 10:23
Try this if(res.getString(res.getColumnIndex("answerquestionid")) != null && !res.getString(res.getColumnIndex("answerquestionid")).trim().equals("")) — Raghavendra, Nov 14 '16 at 10:23
@Raghavendra this one is return error `!res.getString(res.getColumnIndex("answerquestionid")).trim(‌).equals("")` but first one is ok can you provide it as answer so i can close the OP? — Brownman Revival, Nov 14 '16 at 10:28

Raghavendra · Accepted Answer · 2016-11-14T10:33:42.540

1

Try this,

if(res != null){
    if(res.getString(res.getColumnIndex("answerquestionid")) != null && !res.getString(res.getColumnIndex("answerquestionid")).trim(‌).equals("")) 

//your stuff

}

edited Nov 14 '16 at 10:33

answered Nov 14 '16 at 10:29

Raghavendra

2,305
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i am getting error if i include this `&& !res.getString(res.getColumnIndex("answerquestionid")).trim(‌).equals("")` any idea? – Brownman Revival Nov 14 '16 at 10:32
Looks like res.getString(res.getColumnIndex("answerquestionid")) is null so u need to do a null check before accessing trim() method – Raghavendra Nov 14 '16 at 10:34

score 0 · Answer 2 · answered Nov 14 '16 at 10:26

0

Try this:

if(res.getString(res.getColumnIndex("answerquestionid"))!=null){

answered Nov 14 '16 at 10:26

DLIK

50
7

Hughzi · Answer 3 · 2016-11-14T12:46:46.133

0

You are checking the value of something which may be null, which will throw a Null object reference. to fix this you must check if the String is null.

if (res != null) {
     String str = res.getString(res.getColumnIndex("answerquestionid"));
    if(str != null) {
       // Perform action
    } else {
      // String is null so recover (use placeholder, try again etc)
    }
}

alternativley you can do it in one if statement but I find the above more readable.

if (res != null) {
    if( res.getString(res.getColumnIndex("answerquestionid")) != null &&
        res.getString(!res.getColumnIndex("answerquestionid")).trim().equals("")) {
        //Safe to use String
    }
}

edited Nov 14 '16 at 12:46

answered Nov 14 '16 at 10:26

Hughzi

2,470
1
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What if res.getString(res.getColumnIndex("answerquestionid")) itself null? – Raghavendra Nov 14 '16 at 10:28
i've removed the call to Trim but it didn't throw the exception in Op's code. i feel your downvote is misplaced here. – Hughzi Nov 14 '16 at 10:30
What if `res` itself is null? – Andrei Olar Nov 14 '16 at 10:30
1

@OlarAndrei you could ask the same in any of the answers, but a valid point all the same – Hughzi Nov 14 '16 at 10:31

score 0 · Answer 4 · answered Nov 14 '16 at 10:27

You have two ways for it:

First is checking if res exists (best approach)

if(res.getIdentifier(myStringName) != 0){
  //do stuff
}

Because if it returns 0 it means it doesn't exists.

Second way is checking if string is null

String myRes = res.getString(myStringName);
if(myRes != null && !myRes.trim().equals("")){
  //do stuff 
}

Your problem was that you were not checking if the String result was null

Hope this helps

Check returned value by res is null

4 Answers4