A DESCRIPTION OF THE PROBLEM :
The javafx.beans.binding.StringExpression class has the methods isEmpty() and isNotEmpty() which are based on the java.lang.String.isEmpty() method. There should be similar isBlank() and isNotBlank() methods for StringExpression based on the String.isBlank() method added in Java 11.

To be consistent, these methods should be accompanied by isBlank(ObservableStringValue) and isNotBlank(ObservableStringValue) methods in the javafx.beans.binding.Bindings class.