Empty check with String[] array

Question

I want to know the best practice for checking whether a string array is empty or not.

String[] name = {"a" , "b"};

if (name == null) {
}

Is this a good practice or there are more best codes for the same?

What do you mean by "boolean value of the String[]?" What do you expect to be true, what do you expect to be false? — David Ehrmann, Mar 04 '14 at 03:28
I think the concept of a "boolean value of String[]" simply doesn't apply in Java. It's not like JavaScript where things are either truthy or falsy. You can check to see whether a reference is null, or whether the elements of an array are null, but that's about all. — ktm5124, Mar 04 '14 at 03:31

score 24 · Answer 1 · answered Mar 04 '14 at 04:14

24

Normally you would want to do something like:

if (arr != null && arr.length > 0) { ... }

for non-empty array.

However, as you may suspect, someone have made utils for such kind of common action. For example, in Commons-lang, you can do something like:

if (ArrayUtils.isEmpty(arr)) {... }

if you do a static import for ArrayUtils.isEmpty, this line can be even shorter and looks nicer:

if (isEmpty(arr)) { ... }

answered Mar 04 '14 at 04:14

Adrian Shum

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org.apache.commons.lang.ArrayUtils this will be more useful IF THE PROJECT IS ALREADY USING **apache package** , normally simple prog dont use that jar distribution – Srinath Ganesh Mar 04 '14 at 06:42
@SrinathGanesh of course whether to use 3rd party lib is the choice of OP but, with modern build tools like Maven and Gradle, I don't see any problem using such lib in simple programs. – Adrian Shum Mar 04 '14 at 07:51

Aditya · Answer 2 · 2014-03-04T04:23:53.440

6

if(name!=null && name.length > 0) {
   // This means there are some elements inside name array.
} else {
   // There are no elements inside it.
}

edited Mar 04 '14 at 04:23

answered Mar 04 '14 at 03:42

Aditya

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`length` in an array is a field, not a method. – Brian Roach Mar 04 '14 at 03:49
@BrianRoach, thanks for pointing out, by mistake I added parenthesis. – Aditya Mar 04 '14 at 04:24
is nullcheck required ?? length already does the job – Srinath Ganesh Mar 04 '14 at 04:35
1

@SrinathGanesh, Yes null check is required, coz if name is null, then name.length will give NullPointerException – Aditya Mar 04 '14 at 05:39
is checking length required ? not null is not suffice ?? – Spartan Jun 13 '17 at 03:17
@thanga Probably, you didn't get the question right. The question is to check whether the array is empty or not. Hence only null check won't suffice, since it will hold true for cases like array with no elements. String [] name = {}; – Aditya Jul 04 '17 at 13:41

Solace · Accepted Answer · 2014-03-04T03:36:07.850

2

To check if a string array is empty...

public boolean isEmptyStringArray(String [] array){
 for(int i=0; i<array.length; i++){ 
  if(array[i]!=null){
   return false;
  }
  }
  return true;
}

edited Mar 04 '14 at 03:36

answered Mar 04 '14 at 03:27

Solace

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score 2 · Answer 4 · answered Mar 04 '14 at 03:49

All arrays in Java have a special field "length" that contains the number of elements in the array, that is array length in other words.

String test( String[] array )
{
    if ( array == null ) {
        return "array is null";
    }
    if ( array.length == 0 ) {
        return "array is empty, meaning it has no element";
    }
    for ( String s : array ) {
        if (s == null) {
            return "array contains null element";
        }
        if (s.length() == 0) {
            return "array contains empty string";
        }
        // or
        if (s.isEmpty()) {
            return "array contains empty string";
        }
    }

    return "array is not null or empty and does not contain null or empty strings";
}

To test whether the array contains a null element or an empty string you need to iterate through it and check each element individually.

Do not forget that the length of array is the special field array.legnth and the length of the string is the function string.length().

Empty check with String[] array

4 Answers4

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