Checking empty string in Java

Question

I don't know what is wrong with the below code.... I am getting input from a textbox and putting the input in a string. If the textbox is empty it will return a empty string. In the below code

   String[] str = new String[9]; 
   for(int i=0;i<9;i++){
       if(str[i].equals("")){
          System.out.println("set " + cmds[i] + " " + str[i]);
          WriteThread.sendCommand("set " + cmds[i] + " " + str[i] + "\n", false);
       }
    }

In the above code str[i] stores the input text of textboxes and I am trying to check if any element of the array is empty. I also tried with str[i] == "" and str[i] == null but no luck. The statement inside the if block if i am printing the string str[i], it shows nothing that means it is empty.

Am I doing anything the wrong way?

What's that you are trying to check ? You check if the string is empty and then do a print, and the result as you say is something like "set" +... since you can't see an empty string :). Probably you want to test the not condition: i.e if(!str[i].equals("")) .. — sateesh
– sateesh, Commented Dec 24, 2009 at 6:19
Do you think you could edit your question to make it more understandable? From the comments and answers, I can see I'm not the only one that is not sure what you really want... :-( — KLE
– KLE, Commented Dec 24, 2009 at 7:07
Sorry for typo mistake. Actually that was as you hav mentioned the not condition. — Surjya Narayana Padhi
– Surjya Narayana Padhi, Commented Dec 24, 2009 at 7:34
not resolving the problem, but it usually preferred to write if("".equals(str[i])) to avoid NullPointerExceptions — chburd
– chburd, Commented Dec 24, 2009 at 8:05

fastcodejava · Accepted Answer · 2009-12-24 06:14:47Z

27

You could try :

if (str[i] == null || str[i].trim().equals("")){
// your code
}

answered Dec 24, 2009 at 6:14

fastcodejava

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Comments

Romain Linsolas · Accepted Answer · 2009-12-24 06:47:11Z

15

You can use the Apache Commons Lang to check a String:

if (StringUtils.isBlank(str[i]) {
    ...
}

StringUtils.isBlank is checking if the String is null or empty (i.e. if it is equals to "" when all blank characters are removed).

answered Dec 24, 2009 at 6:47

Romain Linsolas

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2 Comments

Jony Over a year ago

what happens if someone just enters space?

Romain Linsolas Over a year ago

@AshishDonvir StringUtils.isBlank(" ") returns true. If you want this test to return false, you can use StringUtils.isEmpty(...) instead.

Martijn Pieters · Accepted Answer · 2020-10-31 14:18:22Z

1

I would recommend

if (str[i] == null || str[i].trim().length==0){
// your code
}

or Java 6 onward

if (str[i] == null || str[i].trim().isEmpty()){
// your code
}

Instead of using equals() because equals() method is overkill to test for an empty String

edited Oct 31, 2020 at 14:18

Martijn Pieters

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answered Jun 29, 2014 at 9:56

pardeep131085

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Comments

GrayWizardx · Accepted Answer · 2009-12-24 06:17:51Z

0

The above code only executes if the string is empty, is that the desired behavior? Also declaring str as new right before the loop pretty much guarantees it will be empty.

If you are trying to assign the values from textboxes you will need to have those assignments somewhere before the loop.

answered Dec 24, 2009 at 6:17

GrayWizardx

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Comments

algernon · Accepted Answer · 2009-12-24 07:23:03Z

0

I actually tried to run your code snippet and got a NullPointerException on your conditional

str[i].equals("")

str[i] == null worked for me. Are you sure you put the right code in your question. It seems odd to be testing for an empty string of an empty array you just initialized.

answered Dec 24, 2009 at 7:23

algernon

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Comments

Saqib S · Accepted Answer · 2015-11-11 19:50:54Z

0

A very simple solution can be like this.

if(str[] != null && !str[].equals(""))

edited Nov 11, 2015 at 19:50

answered Nov 11, 2015 at 19:45

Saqib S

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