3 ms·

Null is the absence of a value. How do to distinguish 0 from no value?

• Maxatar 2y ago
  The point is to eliminate the idea of an absence of a value. A variable is always assigned to a value, but there is a special value called null which behaves as a kind of sentinel value whose methods all return the null value for their respective type.
  • coin 2y ago
    > The point is to eliminate the idea of an absence of a value The whole point is to track the absence of a value. Why would one want to eliminate it? null is way more trackable that some other special value like 0, -1, 999, "", etc.
  • alkonaut 2y ago
    Yes - but as we keep repeating - if you do that why would you use null as a possible state to begin with? Not specific to Java, but in general. E.g a boolean in java has two states true/false while a Boolean with capital B has 3 states true/false/null. In that context you can choose type to represent how many states you have. E.g if it’s a field representing a cache of a bool value you can represent “not yet calculated” with null. It you were to magically convert null to false for a Boolean it only has two states! It’s now unusable for the purpose.
  • Dylan16807 2y ago
    You can do that with some types, but making 0 be that sentinel is completely bonkers. You need a 257th value to have a byte sentinel.