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()

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.!

The library you want to use is the org.apache.commons.lang.StringUtils and you have to add it to your classpath manually or add it as a dependency to your gradle configuration or any other build tool you are using.

IntelliJ does not know the library out of the box as it is not part of the JDK.