public boolean getAsBoolean() {
        switch (this) {
            case FALSE : return false;
            case TRUE  : return true;
            default :
                throw new NoSuchElementException(
                    "Attempted to get value from empty OptionalBoolean."
                );
        }
    }
If a value is present, and the value matches the given predicate,
return a {@code BooleanOptional} describing the value, otherwise return an
empty {@code BooleanOptional}.

@param predicate a predicate to apply to the value, if present
@return a {@code BooleanOptional} describing the value of this {@code BooleanOptional}
if a value is present and the value matches the given predicate,
otherwise an empty {@code BooleanOptional}
@throws NullPointerException if the predicate is null
common-parent/function/src/main/java/com/speedment/common/function/OptionalBoolean.java