StringUtils.isBlank() vs String.isEmpty()

Question

I ran into some code that has the following:

String foo = getvalue("foo");
if (StringUtils.isBlank(foo))
    doStuff();
else
    doOtherStuff();

This appears to be functionally equivalent to the following:

String foo = getvalue("foo");
if (foo.isEmpty())
    doStuff();
else
    doOtherStuff();

Is a difference between the two (org.apache.commons.lang3.StringUtils.isBlank and java.lang.String.isEmpty)?

Answer 1

StringUtils.isBlank() checks that each character of the string is a whitespace character (or that the string is empty or that it's null). This is totally different than just checking if the string is empty.

From the linked documentation:

Checks if a String is whitespace, empty ("") or null.

 StringUtils.isBlank(null)      = true
 StringUtils.isBlank("")        = true  
 StringUtils.isBlank(" ")       = true  
 StringUtils.isBlank("bob")     = false  
 StringUtils.isBlank("  bob  ") = false

For comparison StringUtils.isEmpty:

 StringUtils.isEmpty(null)      = true
 StringUtils.isEmpty("")        = true  
 StringUtils.isEmpty(" ")       = false  
 StringUtils.isEmpty("bob")     = false  
 StringUtils.isEmpty("  bob  ") = false

Warning: In java.lang.String.isBlank() and java.lang.String.isEmpty() work the same except they don't return true for null.

java.lang.String.isBlank()

java.lang.String.isEmpty()

Answer 2

The accepted answer from @arshajii is totally correct. However just being more explicit by saying below,

StringUtils.isBlank()

 StringUtils.isBlank(null)      = true
 StringUtils.isBlank("")        = true  
 StringUtils.isBlank(" ")       = true  
 StringUtils.isBlank("bob")     = false  
 StringUtils.isBlank("  bob  ") = false

StringUtils.isEmpty

 StringUtils.isEmpty(null)      = true
 StringUtils.isEmpty("")        = true  
 StringUtils.isEmpty(" ")       = false  
 StringUtils.isEmpty("bob")     = false  
 StringUtils.isEmpty("  bob  ") = false

Answer 3

StringUtils isEmpty = String isEmpty checks + checks for null.

StringUtils isBlank = StringUtils isEmpty checks + checks if the text contains only whitespace character(s).

Useful links for further investigation:

• StringUtils isBlank documentation
• StringUtils isEmpty documentation
• String isEmpty documentation

Answer 4

StringUtils.isBlank() will also check for null, whereas this:

String foo = getvalue("foo");
if (foo.isEmpty())

will throw a NullPointerException if foo is null.

Answer 5

StringUtils.isBlank also returns true for just whitespace:

isBlank(String str)

Checks if a String is whitespace, empty ("") or null.

Answer 6

StringUtils.isBlank(foo) will perform a null check for you. If you perform foo.isEmpty() and foo is null, you will raise a NullPointerException.

Answer 7

StringUtils.isBlank() returns true for blanks(just whitespaces)and for null String as well. Actually it trims the Char sequences and then performs check.

StringUtils.isEmpty() returns true when there is no charsequence in the String parameter or when String parameter is null. Difference is that isEmpty() returns false if String parameter contains just whiltespaces. It considers whitespaces as a state of being non empty.

Answer 8

public static boolean isEmpty(String ptext) {
 return ptext == null || ptext.trim().length() == 0;
}

public static boolean isBlank(String ptext) {
 return ptext == null || ptext.trim().length() == 0;
}

Both have the same code how will isBlank handle white spaces probably you meant isBlankString this has the code for handling whitespaces.

public static boolean isBlankString( String pString ) {
 int strLength;
 if( pString == null || (strLength = pString.length()) == 0)
 return true;
 for(int i=0; i < strLength; i++)
 if(!Character.isWhitespace(pString.charAt(i)))
 return false;
 return false;
}

Answer 9

I am answering this because it's the top result in Google for "String isBlank() Method".

If you are using Java 11 or above, you can use the String class isBlank() method. This method does the same thing as Apache Commons StringUtils class.

I have written a small post on this method examples, read it here.