It looks like the most readable solution to me and makes it most obvious that the parameters could be empty/null to future maintainers. Just remember that Optional.of(null) will throw a NullPointer exception, while Optional.ofNullable(null) will result in Optional.empty(). Our team work realy hard to produce quality content on this website and we noticed you have ad-blocking enabled. Optional is primarily intended for use as a method return type where there is a clear need to represent "no result," and where using null is likely to cause errors. What does that mean? purpose Maybe type, as much as many people would have liked us to do Reddit, Inc. 2023. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Apparently Optional is only "a limited mechanism to represent a method may have no result". But if you need to map Optional to another Optional youll have an unnecessary wrapper. My take is that Optional should be a Monad and these are not conceivable in Java. (-) Needing to pack an argument in an Optional, is suboptimal for the compiler, and does an unnecessary wrapping. As far as I know, they were voted out of official Java standard (and I don't know if there are any plans to try again). If modelCar is null, it will throw a NullPointer exception. That way, if the Optional is empty, no WHERE param=y is performed. We are on the boundary of the code, which we write ourselves, e.g. Reddit, Inc. 2023. Approach 4: Optional<>. In the original example posted, Optional is used as a method parameter so this is against Java best practices. Stephen Colebourne, mostly known as a principal contributor of Joda-Time and the JSR-310 specification, proposed on his blog post to keep nullable fields inside of a class, but wrap them up with Optional when they leave the private scope through public getters. H2 This code makes silent errors and can confuse you in the future. It could mean theres nothing to return or that an error occurred during execution. This way, it's clear that null values are allowed. In this cases you could either use the boxed variant of int and long or you could use some magic constants to communicate a missing values in hope, the chosen value will never be a real result. I believe that for high-level languages, (of which Java certainly aims to be one,) this question was settled a long time ago. Most developers use maps and thats fine for most cases. @Ajax I think you're misunderstanding the article. For example Optional is passed through mappers and flattened along the way. findfirst If I have a method with one or two optional arguments I try to redesign it using overloads, inheritance etc. Archived post. The wrapper method looks like this: So suppose you have a getter like this: String getName(). jpa java8 - Optional- How to use it correctly? I understand why this could be a problem. The advantage is that it slightly improves understandability of the intent (and does not have disadvantages of other approaches, like external dependencies or performance penalty). I personally don't like doing that but I'd like to hear some opinions. returns an array of results, or a list of results; instead return an Typo in cover letter of the journal name where my manuscript is currently under review. Even so, beware that Guava Optional and Java's Optional aren't interchangeable. Actually, the. java8 - Optional- How to use it correctly? cause errors. (-) Using Optional parameters causing conditional logic inside the methods is literally contra-productive. You could use Guavas Optional instead. Scan this QR code to download the app now. Here we go: One common excessive use of Optional is when we try to use it in the traditional way by assigning null to an Optional: If you need something like the above, its better to assign it to empty or not use it: Keep in mind that Optional is essentially a wrapper, so using it within a constructor adds unnecessary complexity: It is not recommended to create an Optional of a list since if the list is null, Optional would also be null, and its handling becomes more complex. When a method can accept optional parameters, its preferable to adopt the well-proven approach and design such case using method overloading. ChatGPT) is banned, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Passing Optional arguments to Java methods. Was it a cache miss? java.time You only return the Optional if it's absent from the fooService. These objects are wrappers for other objects or primitives to express the fact that a value can be. Please help us improve Stack Overflow. Microservices This is my point of view on this topic. Brian Goetz. In some cases, you could communicate a missing value using 0 or negative numbers, but perhaps this could be a valid value as well, making it even harder to check, whether the value is present. Java programmers should focus on clean code, portability, testability, good architecture, modularity, etc., and not on "Optional is more costly that null reference". Scala does the same as well and no one thinks about nulls. Its quite common to misuse these two concepts. It's interesting to get a bit more insight from the language designers. Archived post. Especially since serialization in Java does have much more pitfalls. Mixing these two levels of abstraction doesn't facilitate legibility so you're better off just avoiding it. (I said "in this regard"; in other regards, Java is better; but that's off-topic right now. I really hope to understand, why this decision was made in Java. Can someone show an alternative using RxJava2? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, If you used optionals, wouldn't you have to check that the optional passed as a parameter isn't, Yes, but it would make it obvious to some one else maintaining the code in the future that the parameter can be empty/null, therefore potentially avoiding a null pointer exception in the future. If Optional<> is appropriate, then I see no reason not to use it. So, I think that's not a good reason. What I have been doing, which has served me well as a rule of thumb. If you can avoid orElseThrow that's also a good practice. Lets see an example: The previous one would be a better option; you can see that the code is quite similar, but computationally speaking, youre creating an unnecessary wrapper, which is more costly for the compiler. : we read from the DB, Rest Endpoint, parse file etc. For more information, please see our Before Java 8, receiving a null value from a method was ambiguous. Besides all the reasoning about modifying the code and forgeting to modify the documentation is still valid. The whole thing is worth a watch, but he addresses Optional<T> as an argument here: . In functional programming you deal with pure and higher order functions that take and compose their arguments only based on their "business domain type". If you have practical experience with Optional, especially as POJO fields or getter outputs, Id be glad to read about what youve learned. Why? Well, that's ONE of the reasons it was added to Java. Subscribe for limitless reading experience: https://zivce.medium.com/membership, Foo getMeFoo(String fooId) throws IllegalStateException {, Optional calcAs(int a) {return Optional.of(a+1);}, jshell> Optional.of(1).flatMap(a -> calcAs(a).flatMap(b -> calcAs(b))), jshell> Optional.of(1).map(a -> calcAs(a).map(b -> calcAs(b))), getMeFoo("123").map(Foo::getXProp).orElse(DEFAULT_VALUE), thisOptional.isPresent() ? Our intention was to provide a limited mechanism for library method return types where there needed to be a clear way to represent no result, and using null for such was overwhelmingly likely to cause errors. The point is to avoid Optional fields in records. replaceAll In the original example posted, Optional<Y> is used as a method parameter so this is against Java best practices. I could see, that it's "more the Java way", to use null whenever some value is not present. We should avoid returning a method with an Optional. The Optional type is highly expressive in this situation and prevents automatic behavior from occurring. Also having to box values in optionals and having to use Optional.empty() for nulls to call a method is messy and makes the call harder to read. By accepting all cookies, you agree to our use of cookies to deliver and maintain our services and site, improve the quality of Reddit, personalize Reddit content and advertising, and measure the effectiveness of advertising. Youd then look at Optionals as a mere tool for mapping further. integration test The other argument I see, is that Optional was not designed to be used in this way. parsing some information may be optional. As to your question whether you should actually do it or not is based on your preference, but as others said it makes your API ugly to say the least. However, as Technically, an Optional is a wrapper class for a generic type T, where the Optional instance is empty if T is null. I.e. You cannot check against tis and you shouldn't check against this. Although the definition of the type on Javadoc is quite descriptive, when it comes to identifying valid use cases its getting more problematic. But such statement is only good in a school-book. if there are millions of the objects to be processed). News, Technical discussions, research papers and assorted things of interest related to the Java programming language In this post, we will discuss Java Optional and best practices, as using Optional correctly is not an option ;). Can you work in physics research with a data science degree? Result: It does not really work. scalability Uncle Bob definitely wouldnt be proud of such code . Also it adds a bit of boilerplate, even thoough I personally find, use of Optional.empty() and Optional.of() to be not so bad. In my opinion, this argument is somewhat valid, but its not a reason to actively discourage the use of Optional. Unfortunately this explanation doesn't address the concern of when the caller is e.g. As usual in programming, theres no one best way to tackle the problem. empty array or list. Every comment is highly appreciated, so dont hesitate to share your observations. Kotlin optional parameter with Java backwards compatibility. Even so, beware that Guava Optional and Java's Optional aren't interchangeable. Does every Banach space admit a continuous (not necessarily equivalent) strictly convex norm? Typically, you will do it by adding a check (condition) based on the Optional.isPresent () method. What are the advantages and disadvantages of the callee versus caller clearing the stack after a call? Perhaps it would be better to say this is API implementor vs API user :). Do modal auxiliaries in English never change their forms? Valhalla wont enable using optional as a field. What is the significance of Headband of Intellect et al setting the stat to 19? Accepting Optional as parameters causes unnecessary wrapping at caller level. java.util.Objects vs Optional which is preferable? What is the reasoning behind the USA criticizing countries and then paying them diplomatic visits? Asking for help, clarification, or responding to other answers. next In Java, the 'Optional' class is a container object used to represent the presence or absence of a value. Why have multiple version of Optional in Java 8. So an Object which has a member of type Optional, is not Serializable as well. ), The only proper alternative to explicit nullability of reference types is the Optional type. Besides having explicit decoration (e.g. Replacing long chains of nested 'if' statements which traverse into a data structure with a single sequence of chained calls to Optional.map is my personal favorite. But there are certain disadvantages : (e.g. When such code is externalized into a separate class, it becomes an optional runtime dependency. How to add a specific page to the table of contents in LaTeX? To illustrate the problem, examine the following constructor declaration: At first glance it may look as a right design decision. Do I have the right to limit a background check? remove Not the answer you're looking for? Advertisement (adsbygoogle=window.adsbygoogle||[]).push({}); The first possible use case is actually a no-brainer. For example, you probably should never use it for something that Orchestration *, Spring Data optional parameter in query method. Interceptor If Java did support true value types, then Optional would have been implemented as a single machine word, which would mean that the runtime overhead of using it would be zero. Java Optional why not an ifNotPresent method? Should Java 8 getters return optional type? Privacy Policy. Now, if you decide to go along this path, your solution will not be the most performant solution possible, because you will be allocating lots of instances of Optional. parameter, but imagine having two or three. Was there a cache hit that happens to be an empty collection? "suboptimal for the compiler": Premature optimisation is the root of all evil if you aren't writing performance critical code (which is often the case when trying to specify a clean interface), this shouldn't be a concern. Optional in the future will be a value-based class, but still, have the Optional traits. For lower versions, you'd need to map the value to Optional. Optional doesnt provide any additional value and only complicates client code, hence it should be avoided. For instance, the Jackson development team has already provided an additional module that handles Optional fields while converting a POJO into JSON format. ssl On the other hand, the result is passed from the API developer to the user. sql graalvm Not great practice, as youre using an empty Optional to swallow the error. You can't just simply implement the Serializable interface and are done. And I think kotlin too, @biziclop yes, an unavoidable point already criticized. Now in a codebase that wants to use solution 2 we get NPE every couple of weeks, so it can't be better, sorry. The advantages are obvious: So in my point, there is no black-and-white in regard of any methodology including this one. Book or a story about a group of people who had become immortal, and traced it back to a wagon train they had all been on, Python zip magic for classes instead of tuples, Extract data which is inside square brackets and seperated by comma. Besides, developers tended to forget verifying if the result was null, which led to nasty NullPointerException at runtime. Passing a null Optional reference can be considered a programming error (because Optional provides an, I'm sorry, but I cannot agree with the argument "wasn't designed" or "somebody recommends against it". It should not be used for getters, lists, or wrapping any object. Save my name, email, and website in this browser for the next time I comment. clumsy. Is Y present? I have done it in a 100k-lines-of-code project. So the answer is specific to Optional: it isn't "a general purpose Maybe type"; as such, it is limited, and it may be limited in ways that limit its usefulness as a field type or a parameter type. What's the use case for Optional flatMap? Approach 4: Optional<>. And this for sure isnt what Optional was meant to do in the first place. So, the question that it ultimately boils down to is: Do you want perfect clarity and type safety in your code, or do you prefer maximum performance? application context As seen in the previous example, you get optional and resolve with orElseThrow. With this in mind, I could use the following method signature and add a clear Javadoc comment to specify that the arguments may be null, hoping future maintainers will read the Javadoc and therefore always carry out null checks prior to using the arguments (solution 2): Alternatively I could replace my method with four public methods to provide a nicer interface and make it more obvious p1 and p2 are optional (solution 3): Now I try writing the code of the class which invokes this piece of logic for each approach. Disclaimer: what I write below is not really an answer to the original question, but rather my thoughts on the topic. Like making all parameters final. Although the disadvantage is non-negligible, it is also not severe. I first retrieve the two input parameters from another object which returns Optionals and then, I invoke calculateSomething. If we want to verify the absence of the result, each collection has the isEmpty() method and in case of arrays, the length property can be used. The ArrayList implementation for example does the same as its contents aren't guaranteed to be Serializable. Instead of having to go through multiple steps to retrieve a value, we can use lambda expressions to chain operations and obtain the value. For example, you probably should never use it for something that returns an array of results or a list of results; instead, return an empty array or list. Suppose you have two not-null strings (ie. Optional was written for functional programming. database And avoid the value!=null Optional trait. Until Oracle actually makes a. Well, the reason for me is: explicit is always better, than implicit. Therefore, if solution 1 is used the calling code would look like this: if solution 2 is used, the calling code would look like this: if solution 3 is applied, I could use the code above or I could use the following (but it's significantly more code): So my question is: Why is it considered bad practice to use Optionals as method arguments (see solution 1)? If X and Y are present, I'll have to call overloaded method C." And so on. code smell that indicated a leakage of control flow from the caller to (Ep. People are lazy to write and read the docs. Ok, I searched, what's this part on the inner part of the wing on a Cessna 152 - opposite of the thermometer. It's a lot harder to ignore Optional than it is to ignore an annotation that you will only notice if reading the docs / source or if your tooling can catch it (static analysis can't always determine nullability correctly). While putting a nullable method result inside Optional is advisable, the rule doesnt apply when the output is a collection or an array. Is the part of the v-brake noodle which sticks out of the noodle holder a standard fixed length on all noodles? Is there a deep meaning to the fact that the particle, in a literary context, can be used in place of . But as always you could simply override the default serialization process or choose not to serialize the Optional field by marking it as transient. Can't find @Nullable inside javax.annotation. In real life there are different situations. Assuming you have something like the following: You could write a function like this that would seem to fit your use case: Thanks for contributing an answer to Stack Overflow! I'll have to call overloaded method B. Optional does not have to add overhead, it only does so in Java. But in this case, I don't see a reason, why it should only be limited to the return type of methods. super T, ? date I think in such cases it might be useful to have optional as parameters. So what are your opinions on using optionals as parameters? Therefore forcing someone to take an existing object and wrap it in an optional is sort of pointless. Can Visa, Mastercard credit/debit cards be used to receive online payments? You should almost never use it as a field of are used). Since Java 8 appeared a few years ago, along with the introduction of Optional, I have seen many instances of misuse or incorrect use of Optional. And if you find that you need to focus on micro-optimizations, then you'd better skip Objects, Lists, Generics and switch to arrays and primitives (I don't want to be offensive here, I'm just sharing my opinion). But eventually it comes down to a design decision that was made. The arguments against this rely on arguments from authority (see Brian Goetz - his argument is we can't enforce non null optionals) or that the Optional arguments may be null (essentially the same argument). Maybe monad. There are plenty of others. Passing a parameter with Optional in a method is counterproductive as it requires adding conditional logic to handle this parameter. Guava Optional has the or method for lower Java versions if that's what you need. (And it is arguably even slightly better, because with Optional you can indicate optional-of-optional if you must, whereas with explicit nullability you cannot have ReferenceType? For example, you probably should never use it for something that returns an array of results, or a list of results; instead return an empty array or list. Besides lately the trend is, that we should avoid writing documentation in favor of making the code itself self-describing. "Not handling null" could only realistically mean an exception is thrown. Optional as a parameter is bad practice. In case when theres no element to return, an empty instance is superior to empty Optional and null as it conveys all necessary information. To be clear, you should avoid these worst practicesand eliminate them when you maintain or refactor existing code. extends Optional is used to force the developer to handle null values. The 'Optional' class does not support the 'List' type, so you cannot use 'Optional<List>' in Java. Cookie Notice But well wait for Valhalla to see how will that work. Still, people have issues with Optional usage. annotation or type) could help static analyzer (or compiler) to catch some null-pointer related issues. Theres nothing wrong with Optional that it should be avoided; its just not what many people wish it were, and accordingly, we were fairly concerned about the risk of zealous overuse. Is it a good idea to use Optional instead of overloading? Note theres only one optional parameter, but imagine having two or three. I worked in a codebase like that for 2 years and we never got a NPE. Optional doesn't provide any additional value and only complicates client code, hence it should be avoided. Regarding the last paragraph, my convention is a post-fix. Relativistic time dilation and the biological process of aging. No matter what your team decides when starting a new application, the best advice is to keep it consistent across the whole project. Why would one need to declare variables as nullable/non-nullable? Streams need it. The pattern with Optional is for one to avoid returning null. There are almost no good reasons for not using Optional as parameters. Finally someone said it, use of Optional introduces a performance penalty. Heres what this would look like: Another example you may see is empty Optional on exceptions. I know that this question is more about opinion rather than hard facts. Even so, this operator is available only for Java 9 and above. so. What does that mean? They are computationally less expensive, simplify the code, and are considered best practices: In this post, we have tried to analyze the options we have with Java Optional and best practices to make better use of Optional. rev2023.7.7.43526. A developer is responsible for providing a precise specification and a correct implementation. Before applying the type, all possible alternatives should be considered as overusing of Optional may lead to introducing new burdensome code smells. This adds the default Optional behavior to it. At first, I also preferred to pass Optionals as parameter, but if you switch from an API-Designer perspective to a API-User perspective, you see the disadvantages. Spring Data When a method can accept optional parameters, its preferable to adopt the well-proven approach and design such case using method But I recently moved from being a .net developer to a java one, so I have only recently joined the Optional party. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. And the only source for it is my thoughts and my experience (with Java and other languages). Reddit and its partners use cookies and similar technologies to provide you with a better experience. But there are also drawbacks, like: there is no tooling to support this convention (your IDE will not show you any warning, if you access "maybe"-variable without first checking it). Actually just use the NonNull/Nullable annotations, that's what you're looking for in this situation, not optional.
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