Hence better suited for result than input, for the complexity of the data flow. To quote the original author: This argument refers to a situation when you use Optional as a method parameter just to do conditional logic based on its presence: It is an argument, but a limited one. And with all that being said, lets once again imagine having two or three.. Then, if a client has a potential null on his side, hes forced to do the conditional logic himself: This, depending on the case might be a good thing or a bad thing. After all, we For the sake of simplicity let't not consider primitive types in further discussion, so I will claim simply that all variables are nullable. rev2022.7.21.42635. I know that this question is more about opinion rather than hard facts. First of all, if you're using method 3, you can replace those last 14 lines of code with this: int result = myObject.calculateSomething(p1.orElse(null), p2.orElse(null)); The four variations you wrote are convenience methods. null, which you shouldnt pass around for some boundary value like MAX_INT. I dont like the idea of passing nullable params neither. The first limitation that I see is that oftentimes you would not do any conditional logic on the argument you just want to pass it through: The second limitation is that the only reasonable alternative that you have in most cases is method overloading. something or a method parameter. Is to use Optionals for return types, and only use Optionals as parameters, if I require both the value of the Optional, and weather or not the Optional had a value within the method. Too many unnecessary validations. Using an optional does not really enable you to write your method logic more neatly. Approach 2: Use documentation and/or comments to describe, which arguments/fields are nullable and which not.

empty array or list. : we read from the DB, Rest Endpoint, parse file etc. Let me augment those with some of my recent reasoning. It's still perfectly possible to pass in null to a method. Everything you would have to do all the time you in fact should (almost) never do. For example I have a piece of logic which has 2 optional parameters. I'll have to call overloaded method B. Id say that you should apply common sense and other known guidelines to figure out whats the best in such case. the callee, it should be responsibility of the caller to check the That said, in practice, I've rarely found using Optional as a field type or a parameter type to be an issue. In Java, Varargs (variable-length arguments) allows the method to accept zero or multiple arguments. I used "maybe"-prefix, so that if e.g. Lets say that our method (and the private ones that it calls) has two testable side-effects and one error case in which it throws an exception. 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. Obviously not. Asking for help, clarification, or responding to other answers. Also, I'd prefer to state this as a comment, but since my point level does not allow me to comment, I am forced to put this as an answer instead. Using @Nullable is much worse tham using Optional, because Optionals are much more verbose from an API point of view. The wrapper method looks like this: So suppose you have a getter like this: String getName(). The advantages are obvious: So in my point, there is no black-and-white in regard of any methodology including this one. This adds the default Optional behavior to it. I'm not sure what ambiguity there is @user2986984.

That's also the best approach. Using Optional as parameters might be useful in some use cases which involves protobufs or setting fields in a configuration object. Edit: Approach 5: I used this one recently, when I could not use Optional. "suboptimal for the compiler", "In comparison to nullable parameters Optional is more costly" - these arguments could be valid for C language and not for Java language. First let's check, why would anyone like to use Optional at all? But such statement is only good in a school-book. Which @NotNull Java annotation should I use? I don't see any good reasons against using Optionals as arguments (provided you don't want to use method overloading). Is Y present? API receiving the proto request would handle the different fields. Is that bad for your codebase? Site design / logo 2022 Stack Exchange Inc; user contributions licensed under CC BY-SA. If you stablish that in your codebase there are no nulls (in every boundary with external libs you ensure that), then you can rest assured there are no nulls. What I have been doing, which has served me well as a rule of thumb. Can't return values and fields be null as well? But some people don't want to provide all the data. However there are a bunch of possible reasons why you would want to require an Optional argument nonetheless: Check out the JavaDoc in JDK10, https://docs.oracle.com/javase/10/docs/api/java/util/Optional.html, an API note is added: API Note: Movie about robotic child seeking to wake his mother. The best post I've seen on the topic was written by Daniel Olszewski: Although it might be tempting to consider Optional for not mandatory method parameters, such a solution pale in comparison with other possible alternatives. Note theres only one optional java.util.Objects vs Optional which is preferable? You can pass a getter that doesn't return Optional to a method like flatMap(), by wrapping it in a another method that converts the function to the right type. This advice is a variant of the "be as unspecific as possible regarding inputs and as specific as possible regarding outputs" rule of thumb. The API should be as simple as possible to the user, and null is the simplest. That way, if the Optional is empty, no WHERE param=y is performed.

Why are Java generics not implicitly polymorphic? for calling the constructor, client code can become a little bit You cannot check against tis and you shouldn't check against this. See the original article here. Such a good movement, but sometimes we tend to overdo things. If you have any additional arguments for or against using Optional as method parameter type, let me know in comments! Your use of p1.orElse(null) illustrates how verbose our code gets when using Optional, which is part of why I avoid it. So, IMO discussion above shows, that even though mostly we can survive without nullable arguments, but sometimes it is not really feasible. Id say that you should keep each of them in the back of your head and evaluate things on a case by case basis. If we followed this logic, wed have to say that using Java is unsafe as you can do almost anything via reflection. (-) In comparison to nullable parameters Optional is more costly. overloading. Thus it takes default values for optional parameters. Disclaimer: what I write below is not really an answer to the original question, but rather my thoughts on the topic. If I cannot find the solution in reasonable time, I start thinking, if the performance is critical (i.e. Am I wrong, or @Nullable is not in part of java standard? Like always, its anit depends problem, and it requires a bit of programming sense. In the User class, there are only getters and no setters to preserve immutability.if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[468,60],'delftstack_com-banner-1','ezslot_5',110,'0','0'])};if(typeof __ez_fad_position!='undefined'){__ez_fad_position('div-gpt-ad-delftstack_com-banner-1-0')}; In the TestUser class, we utilize the UserBuilder to create the User class object. While these aren't really official yet, you can use JSR-308 style annotations to indicate whether or not you accept null values into the function. For me the reason is simple: unlike other languages java does not have built-in capability to define variable (or type) as nullable or not. So that's usually the only good reason for writing a method that returns Optional. Im not so sure if it would be so evil if the logic looked like this: Does it still do more than one thing? If a value is present, then the isPresent() method will return true, and the get() method will return the value.if(typeof ez_ad_units!='undefined'){ez_ad_units.push([[468,60],'delftstack_com-medrectangle-4','ezslot_0',112,'0','0'])};if(typeof __ez_fad_position!='undefined'){__ez_fad_position('div-gpt-ad-delftstack_com-medrectangle-4-0')}; In case if we expect some null values, we can use the ofNullable() method of this class. Another problem is that it only helps, when applied consistently by all people working on the project. There isnt any rule which applies for all the scenarios. parameter, but imagine having two or three. Is moderated livestock grazing an effective countermeasure for desertification? And once youd do that, the callee code could not be modified in any way that does not support null, which is a rather unwanted constraint. There are methods, like Optional.flatMap() method, that requires a reference to a function that returns Optional. super T, ? The way they are treated by different systems are not uniform. But the. In Java class, when we design a method or function, some arguments may be optional for its execution. As Java programmers we should only be using null to interact with legacy libraries. Approach 1: All arguments are nullable (according to java standrd, except primitive types). (instead of occupation of Japan, occupied Japan or Occupation-era Japan). This is the case that weve already seen in the argument about conditional logic. processing of huge amounts of data, so that total execution time is very large, or situations when throughput is critical). If I were to write tests for this method, it would look more or less like this: Thats already a decent amount of code. This. My intuition suggests that this could be the case, but I cant come up with a good example. Is there a faction in the Ukrainian parliament favoring an immediate ceasefire? empty optional / null. And dont forget, there are also arguments for using Optional this way. For example, a cache. Is it bad wiring/low power draw? Let's make something perfectly clear: in other languages, there is no general recommendation against the use of a Maybe type as a field type, a constructor parameter type, a method parameter type, or a function parameter type. parsing some information may be optional. 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. In this cases performance penalty introduced by Optional may be really unwanted. It makes obvious to the reader of the code (or to the user of API), that these arguments may be null. The method isPresent() checks if the value is present; otherwise, the default string is assigned to it, as shown in the code below. People are lazy to write and read the docs. One of the best ways of using this is to have multiple optional parameters and using liftM2 to use a function assuming the parameters are not empty and returning an optional (see http://www.functionaljava.org/javadoc/4.4/functionaljava/fj/data/Option.html#liftM2-fj.F-). The purpose of the Build Pattern is to separate the complex object construction from its representation. Maybe monad. If a class has multiple methods that have the same name but takes different parameters, it is called method Overloading. class only distract the reader. Were done with the arguments against Optional method parameters that I found online. Usually it is not the case. I dont. in a case of library code, you should probably stick to overloading. And of course this is POD, so basically type with value-semantics, so I want it to be more or less immutable (no setters). Mixing these two levels of abstraction doesn't facilitate legibility so you're better off just avoiding it. explicitly marked the attachment parameter as optional. The arguments passed to the methods are different one takes two int type arguments while the other takes three. code smell that indicated a leakage of control flow from the caller to There are some valid arguments against using Optional as method parameter type, but to me, they are not good enough to be able to say with confidence that you should avoid it at all costs. Well, not quite. The majority of articles that I read, and even my fantastic IDE point out, that Optional as a method argument is bad because the original intent of creating Optional was to: Im sorry to say this, but this is a really bad argument. Here the variable lastName is passed null for the Student class object, so we created an Optional object that may contain a null value. Moreover, it forces both: user of the API and developer of the method to aknolage this fact by explicitly wrapping/unwrapping the values (which is not the case, when annotations like @Nullable etc. 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). If Optional<> is appropriate, then I see no reason not to use it. Is "Occupation Japan" idiomatic?

That being said, chaining methods together that take/return optionals is a reasonable thing to do, e.g. Perhaps it would be better to say this is API implementor vs API user :). And I think kotlin too, @biziclop yes, an unavoidable point already criticized. And the only source for it is my thoughts and my experience (with Java and other languages). @Ajax I think you're misunderstanding the article. If you dont know all your clients e.g. This question is the reason why I started the research and then decided to write this article. What drives the appeal and nostalgia of Margaret Thatcher within UK Conservative Party?

Imagine that one of your API parameters is optional and its represented by a null. purpose Maybe type, as much as many people would have liked us to do So we check all of them. If Optional, despite its limitations, works as a parameter type or a field type for your use case, use it. Oh, those coding styles are to be taken with a bit of salt. I first retrieve the two input parameters from another object which returns Optionals and then, I invoke calculateSomething. A safe approach would be to choose one depending on the clients needs. For example, you probably should never use it for something that There are no optional parameters in Java, but we can simulate optional parameters using the following techniques discussed in this article. Instead of stating clearly in the code: This parameter is optional, were adding the complexity of multiple analogous overloads. The logic and default configuration values required to create an object are enclosed in the builder class. Spring Data optional parameter in query method. Besides lately the trend is, that we should avoid writing documentation in favor of making the code itself self-describing. 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). "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. Scala does the same as well and no one thinks about nulls. Why does KLM offer this specific combination of flights (GRU -> AMS -> POZ) just on one day when there's a time change? All "object"-variables are nullable and all primitive-types are not. Consider class, which represents settings of some system, or personal data of some user, or in fact any composite data-structure, which contains lots of fields - many of those with repeated types, and some of the fields are mandatory while others are optional. As far as I remember it was voted out A good API designer always looks from the user perspective. Trending is based off of the highest score sort and falls back to it if no posts are trending. Outside of functional programming, Optionals should be avoided. Faulty AC. Unfortunately this explanation doesn't address the concern of when the caller is e.g. Daniel Olszewski, in his article titled Java 8 Optional Use Cases, argues that the case of Optional method parameters is much worse in the case of multiple such parameters. But yes, that could be a code smell, especially if that one thing would be the conditional logic we talked about earlier. extends Optional Optional flatMap(Function can be null itself. Well, that's ONE of the reasons it was added to Java. In the example of the SystemMessage class, declaring Uncle Bob definitely I'm struggling to find a logical reason why. Instead overloads should be used. returned from some other method): You're forced to wrap them in Optional even if you know they are not Empty. But even there, it can be avoided. The source of this argument is the top answer in a related question on StackOverflow. Optional was written for functional programming. Why is executing Java code in comments with certain Unicode characters allowed? Would that stop you from using Java? If so, I'll call overloaded method A. so. Well, the reason for me is: explicit is always better, than implicit. How should we do boxplots with small samples? So, Regarding the last paragraph, my convention is a post-fix, I think that's not a good reason. Also, when it comes to collections, there is a distinct difference between an empty collection and no collection. [W]e did have a clear To conclude this argument, know your clients! Before we get into the case of using Optional, we should understandwhy we even have this problem. Making statements based on opinion; back them up with references or personal experience. You should only use them when they're more convenient. cause errors. wouldnt be proud of such code . you want your function to be used in conjunction with another API that returns an, Your function should return something other than an empty. If there would be arguments for using Optionalas a parameter type that outweigh the arguments against, it would only mean that the class is better than it intended to be and everyone should be happy. The disadvantages are already mentioned in other comments, the worst of which is (IMO) performance penalty. Is List a subclass of List? The use of this particular approach is not recommended as it creates maintenance problems. (I'm aware the designers of Optional intended it to only be used as a return type, but I can't find any logical reasons not to use it in this scenario). Published at DZone with permission of Grzegorz Ziemoski, DZone MVB. Blondie's Heart of Glass shimmering cascade effect. Java 8 has unfortunately implemented a very limited library supporting optional. when the structure of the data is not developed by ourselves, but is imposed by some external interfaces, db-schemas etc At the end, I think, that one should think about the problem, which is being solved, and try to find the appropriate tools. This way, it's clear that null values are allowed. Brian Goetz said it best when he said this: The reason Optional was added to Java is because this: Irrespective of Java 8, Use old school method overloading technique to bring clarity and flexibility, suppose you have following method with two args, in case you want to add additional optional parameter then overload the method, A good example were Optional as arguments would be nice is JPA Repositories. How do I use optional parameters in Java? Few rules to keep in mind while using varargs is that each method can have only one varargs parameter, and it must be the last parameter. Therefore, you need another solution in case one of the parameters is missing. Result: code explodes with checks, which are mostly unneeded, because as we discussed above almost all of the time we can go ahead with nullable variables, and only in some rare cases "nullables" are needed. So you can introduce ambiguity with such annotations instead of clarity.