StringUtils.isBlank return false for null Strings

Question

I am working in a Java project and my code shows weird behavior. Here is my code:

String access = String.valueOf(getStringvalue());
Boolean isBlank = StringUtils.isBlank(access);

In the above code, 'access' object can have null values. And it is said that if we pass a null value to StringUtils.isBlank(), it will return true. But here I returned only false value when access is null. What is the reason for this behavior?

check the implementation of StringUtils class. It is from apache common utils? — Vishrant
– Vishrant, Commented Nov 24, 2015 at 7:47
If you pass null to String.valueOf you get the string "null". That is not null and it is not blank. — khelwood
– khelwood, Commented Nov 24, 2015 at 7:47

Vish · Accepted Answer · 2015-11-24 08:02:36Z

5

I also had this problem and found the trick just after saw the source code of String.valueof(). The source code of String.valueof() is below.

public static String valueOf(Object obj) {
    return (obj == null) ? "null" : obj.toString();
}

Therefore when you pass a null object, you will get a 'null' String. Therefore your StringUtils.isBlank() will treat is as a String rather than a null object and you will get a 'false' booean value.

Hope it helps.!

edited Nov 24, 2015 at 8:02

answered Nov 24, 2015 at 7:48

Vish

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4 Comments

Jon Skeet Over a year ago

No need to look at the source code - this is the documented behaviour of String.valueOf. It's not clear why the OP is calling String.valueOf at all...

JB Nizet Over a year ago

"null" is a string with 4 characters: n, u, l and l. It's a string, like any other string.

Viswanath Lekshmanan Over a year ago

@JBNizet Nice explanation. So valueOf(null) will return "null" as string ?

JB Nizet Over a year ago

Yes, as documented. docs.oracle.com/javase/7/docs/api/java/lang/…: Returns: if the argument is null, then a string equal to "null"

Abdelhak · Accepted Answer · 2015-11-24 08:03:55Z

0

I tested those code and they give the same result.

 Boolean isBlank = StringUtils.isBlank("");
 System.out.println(isBlank);// give true

and

 Boolean isBlank = StringUtils.isBlank(null);
 System.out.println(isBlank);// give true

edited Nov 24, 2015 at 8:03

answered Nov 24, 2015 at 7:53

Abdelhak

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2 Comments

Stultuske Over a year ago

String s1; is not always the same as String s1 = null; Just try and create a String as a local variable, it doesn't get a default value.

Ivar Over a year ago

println(true) and println("true") will print the same thing, though they are different types. If you pass the same two values to StringUtils.isBlank(), they will give a different outcome.

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