The BooleanDataFormat class contains the following methods:
getFalseValue retrieves the string that is displayed for false values.
getNullValue retrieves the string that is displayed for null values.
getTrueValue retrieves the string that is displayed for true values.
setFalseValue sets the string to be displayed for false values.
setNullValue sets the string to be displayed for null values.
setTrueValue sets the string to be displayed for true values.