StringUtils.isBlank() vs String.isEmpty()

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() (since Java 11)

java.lang.String.isEmpty()

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

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

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

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

will throw a NullPointerException if foo is null.

StringUtils.isBlank also returns true for just whitespace:

isBlank(String str)

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