Creates a new javafx.beans.binding.BooleanBinding that holds true if the value of a javafx.beans.value.ObservableStringValue is less than a constant value.

Note: In this comparison a String that is null is considered equal to an empty String.

Parameters:

op1		the ObservableStringValue
op2		the constant value

Returns:  the new BooleanBinding

Exceptions:

NullPointerException

if the ObservableStringValue is null