public String toString() {
        StringBuilder buf = new StringBuilder();

        buf.append(isLowerBoundInclusive() ? '[' : '(');
        if (getLowerBound() != null) {
            buf.append(getLowerBound().toString());
        }
        buf.append(',');
        if (getUpperBound() != null) {
            buf.append(getUpperBound().toString());
        }
        buf.append(isUpperBoundInclusive() ? ']' : ')');