public ULong add(int val) throws NumberFormatException { return add((long) val); }
public ULong subtract(final long val) { if (val < 0) return add(-val); if (compare(value, val) < 0) throw new NumberFormatException(); final long result = value - val; if (value < 0 && result >= 0) throw new NumberFormatException(); return valueOf(result); } }