!array[0].isEmpty() returning NullPointer?

Question

Here's my code:

if (!quizDescs[0].isEmpty()) {
    mDescText.setText(quizDescs[0]);
} else {
    mDescText.setVisibility(View.INVISIBLE);
}

So, when this code runs, and the if condition returns true, everything is fine and dandy, however, if it returns false, it says there's a NullPointerException, and points me to the line of code containing the if statement.

Am I checking the condition right? Why is it returning a NullPointer?!

ANSWER:

    if (quizDescs[0] == null) {
       mDescText.setVisibility(View.INVISIBLE);
    } else {
       mDescText.setText(quizDescs[0]);
    }

you check if your text is empty but you should also check if your list quizDescsexists. — jhamon
– jhamon, Commented Nov 18, 2014 at 9:16

Murtaza Khursheed Hussain · Accepted Answer · 2014-11-18 09:23:34Z

2

if quizDesc[0] is String, you can do

if(!StringUtility.isEmptyOrNull(quizDesc[0])){
 mDescText.setText(quizDescs[0]);
}else {
    mDescText.setVisibility(View.INVISIBLE);
}

By the way, Null and being empty is not same

Consider

String s; //Initialize to null
String a =""; //A blank string

Its always a good practise to use

try{
   //Your code here..
}catch(Exception e){
    e.printStacktrace();
}

edited Nov 18, 2014 at 9:23

answered Nov 18, 2014 at 9:17

Murtaza Khursheed Hussain

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Comments

Eran · Accepted Answer · 2014-11-18 09:20:54Z

1

If either quizDescs or quizDescs[0] are null, you'll get a NullPointerException.

Obviously, if isEmpty() returns false, it means that isEmpty() was executed, so quizDescs[0] is not null when the condition returns true, and that's why it works.

Either make sure that both quizDescs and quizDescs[0] is never null, or change the condition to :

if (quizDescs != null && quizDescs[0] != null && !quizDescs[0].isEmpty()) {
    ....
} else {
    ....
}

edited Nov 18, 2014 at 9:20

answered Nov 18, 2014 at 9:15

Eran

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Comments

Maxime · Accepted Answer · 2014-11-18 09:18:52Z

0

You have an error because quizDescs is Null so when you try to get quizDescs[0] in the condition, you try to get the first item of null object.

answered Nov 18, 2014 at 9:18

Maxime

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Comments

LastFreeNickname · Accepted Answer · 2014-11-18 10:55:09Z

0

The only possible ways the if-line can cause a NullPointerException, is when quizDescs itself is null or the first element quizDescs[0] is null. Try to extract quizDescs into a local variable for debugging purposes and inspect its content.

You can either initialize your array with empty strings or add a check for null - or better review your logic how null is a possible condition. Usually null values should be avoided (see Bloch, Effective Java 2nd Edition, item 43 for a similar case).

edited Nov 18, 2014 at 10:55

answered Nov 18, 2014 at 9:19

LastFreeNickname

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1 Comment

Thorsten Dittmar Over a year ago

No. The second possible way is that quizDescs itself is null.

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