How to check if String is empty?

Question

I am using following code to check if the String is empty

if( !Index2.toString().isEmpty()){
  ....
}

But I run into following error

java.lang.NullPointerException

Index2.toString().isEmpty() should be Index2!=null && Index2.toString().isEmpty() — Shashank Kadne
– Shashank Kadne, Commented Oct 12, 2012 at 6:40
Hello, Index2 is it your own class? Probably you redefined toString() method, and it returns null now. Which in turn causes NPE. I do not think it's a good idea to have blahblahblah.toString().isEmpty() code, could you please highlight the root of the problem, it could probably be the issue with the method you've choosen, as for example, you are trying to check if index object is filled - it would not be a good idea to check string, it would be rather better to have utility method or instance method which checks. — zubrabubra
– zubrabubra, Commented Oct 12, 2012 at 7:33

Luiggi Mendoza · Accepted Answer · 2012-10-12 06:44:35Z

4

Your Index2 variable has null value. That's why you get the error. Specifically, the error is here:

Index2.toString()

Assuming your Index2 variable is different from null, your code will work. In order to make your code to work, you can validate that your Index2 is different from null or add a try/catch block that handles NullPointerException.

First way:

if( Index2 != null && !Index2.toString().isEmpty()){
    //...
}

Second way:

try {
    if( !Index2.toString().isEmpty()){
      //...
    }
} catch (NullPointerException npe) {
    //handle the Exception...
}

IMHO I would use the first way.

edited Oct 12, 2012 at 6:44

answered Oct 12, 2012 at 6:39

Luiggi Mendoza

85.9k16 gold badges160 silver badges354 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Michael Laffargue Over a year ago

@EmertanaEm Use Exception handling only on exceptional cases, it's time consuming and shouldn't be used in the normal flow of the application

Subhrajyoti Majumder · Accepted Answer · 2012-10-12 06:39:48Z

2

Check Null also.

if( Index2!=null && !Index2.toString().isEmpty()){
  ....
}

answered Oct 12, 2012 at 6:39

Subhrajyoti Majumder

41.3k13 gold badges84 silver badges103 bronze badges

Comments

Pete · Accepted Answer · 2012-10-12 06:42:50Z

2

There's a StringUtils class in the apache.commons package that has lots of useful methods, like

StringUtils.isEmpty(theString)

Which will do both comparisons, != null and isEmpty and looks better.

answered Oct 12, 2012 at 6:42

Pete

10.9k28 gold badges96 silver badges143 bronze badges

Comments

csk · Accepted Answer · 2013-05-03 06:59:16Z

2

Check for String not to be null as well check for the empty space in a String because even if we have a space in a String as myString=" "; myString.isEmpty() will return false . so please considering the case above i will suggest as :

  if (myString != null && myString.trim().length() != 0 ) 
               return true;

answered May 3, 2013 at 6:59

csk

5661 gold badge5 silver badges15 bronze badges

Comments

anubhava · Accepted Answer · 2012-10-12 06:40:31Z

0

This is how you should check empty for your case:

 if( Index2 == null || Index2.toString() == null || 
     Index2.toString().length() == 0)
     // it is empty

answered Oct 12, 2012 at 6:40

anubhava

790k67 gold badges603 silver badges671 bronze badges

Comments

Ravi A · Accepted Answer · 2012-10-12 07:44:05Z

0

isEmpty() and null has nothing to do with each other. First checks the value of String if its equal to "" - OR you can say it will return true if its length is only and only 0. And second is checking for its initialization.

You should check for both of these condition if needed, like this,

if( str != null && !str.isEmpty() ) { ... }

OR

if( str != null && !str.equals("") ) { ... }

OR use this in your case,

if(index2 != null) { if( index2.toString() != null && !index2.toString().isEmpty() ) { ... } }

edited Oct 12, 2012 at 7:44

answered Oct 12, 2012 at 7:21

Ravi A

5251 gold badge5 silver badges16 bronze badges

2 Comments

Ravi A Over a year ago

if you are creating your String from any other object then you can use if(index2 != null) { if( index2.toString() != null && !index2.toString().isEmpty() ) { ... } }

Ravi A Over a year ago

@Emertana Em I've did exactly the same thing in comment. But I gave some explanation too. That's why did you undo Accept ... ?

Collectives™ on Stack Overflow

How to check if String is empty?

6 Answers 6

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

1 Comment

Comments

Comments

Comments

Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related