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What if null was an Object in Java?
81–90 of 164 posts
Re: What if null was an Object in Java?
#82The author is now discovering Ruby and Objective-C :-)
Re: What if null was an Object in Java?
#83I quite like the way dart handles nulls.
The way Crystal and Dart 2 handles it? Null as a separate and unique type unrelated to Object where type unions solve the problem using syntax like `String?` that is equal to `String | Null`.
Re: What if null was an Object in Java?
#84The problem isn't really that null isn't an object, it's that the type system allows any object reference of a particular class to also be null.
After using Typescript for the past couple years, it's such a joy when you define a variable of type Foo and know it won't contain null. Granted, TS also has to deal with undefined vs null weirdness (and even more weirdness in that an object not containing a property is subtly different from that object property being undefined), but in general the support for "optional" typing works very well.
Java tried to add things like the Optional class, but without first-class language support it's just a mess and you have developers doing crazy things, like having a method return an Optional that will sometimes also return null, by design (yes I've actually seen this).
Re: What if null was an Object in Java?
#85I'd like a null on the same order as NaN. You can use it, compute new values with it, call methods on it, but all results are a similar NaV (not-a-value?).
Re: What if null was an Object in Java?
#86I'd like a null on the same order as NaN. You can use it, compute new values with it, call methods on it, but all results are a similar NaV (not-a-value?).
That sounds horrible. Throwing an npe is almost certainly better than just blithely continuing to process broken state.
Re: What if null was an Object in Java?
#87Earlier quoted context omitted.
null would just mean the zero value instead of the absence of a value String foo = null; String bar = ""; foo.equals(bar) --> true This works well provided the data type has a sensible zero value like collection types EDIT: I'm blocked from posting so I won't be responding further, thank you for discussion.
In the end, you'll have a mixture of NULL and "" in your DB, and a couple of years later a piece of logic written in another language will fail spectacularly.
One response to this is issue is a CHECK constraint LENGTH(column) > 0, so you can’t have empty strings.
Rarely do you have a textual database column where the empty-vs-NULL distinction is semantically meaningful in the application domain. Most of the time, either the column value is missing (arguably better represented by NULL) or has a non-blank value. “Present but blank” is rarely meaningful or useful
Sometimes I pair that with (TRIM(column)=column) to prevent leading or trailing whitespace being saved, which also stops all-blank values being saved
This works really well if you have an RDBMS which supports CREATE DOMAIN, so then you can attach these constraints to a user-defined type and don’t have to repeat them for each column, you just set the type of the column to that user-defined type
Re: What if null was an Object in Java?
#88The problem isn't really that null isn't an object, it's that the type system allows any object reference of a particular class to also be null. After using Typescript for the past couple years, it's such a joy when you define a variable of type Foo and know it won't contain null. Granted, TS also has to deal with undefined vs null weirdness (and even more weirdness in that an object not containing a property is subt…
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Re: What if null was an Object in Java?
#89Earlier quoted context omitted.
null would just mean the zero value instead of the absence of a value String foo = null; String bar = ""; foo.equals(bar) --> true This works well provided the data type has a sensible zero value like collection types EDIT: I'm blocked from posting so I won't be responding further, thank you for discussion.
That just gets us back to the problem for which Null is introduced in almost every lamguage: indicating the absence of a value. This is an important feature in every language, and null is the most popular solution to it (the only significant alternative is the Maybe monad). To put this in more concrete terms, if this change were integrated in Java, how would you indicate the difference between a JSON document which d…
I dare say there's a lot more use of a magic value to indicate no value than a distinguishable representation of it :-)
I base this mostly on an assumption of C still being one of the most widely used languages for the code that's running out there in the world. In C, after all, NULL is just a magic value rather than a distinguishable representation of no value, though that's just one example out of a host of others, all the way down to the venerable NUL-terminated string.
As for your question: something like 'keys(jsonobject).contains("fieldName")' ? Or 'NoSuchFieldException' thrown if you do 'jsonobject.get("fieldName")' ?
(The latter of which, given the general uneasiness NullPointerException creates in us devs, is often how a Java API will work anyway! Checked exceptions won the day! Until the Functional interface was made, at least.)
Or to answer it in the same spirit as this overall comment, why would you need to distinguish between missing and empty? Can't you just define the semantics of the document s.t. those two things having the same effect?
Re: What if null was an Object in Java?
#90Earlier quoted context omitted.
null would just mean the zero value instead of the absence of a value String foo = null; String bar = ""; foo.equals(bar) --> true This works well provided the data type has a sensible zero value like collection types EDIT: I'm blocked from posting so I won't be responding further, thank you for discussion.
In the end, you'll have a mixture of NULL and "" in your DB, and a couple of years later a piece of logic written in another language will fail spectacularly.
It took many years to eliminate all the instances of "NULL" from the database.