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While programming, we have all faced the most in famous NullPointerException. And I believe we all would agree that encountering NullPointerException is also a pain. Just to keep the readers informed, the famous computer scientist Tony Hoare introduced null references and he thinks this as A million-dollar mistake. Just to give a context - an employee can own a car not mandatory though , a car can have insurance not necessarily and an insurance must have a name always.
Just keep it mind to understand the folloiwng sections. We also feel this also pollutes the source code and according to my opinion, it should be considered as an antipattern. Such deep nesting for null checks as mentioned in the previous section looks a bit obtruse. And sometime people do it in different way. But still it follows the same antipattern to check for nulls in a bit different way. Few languages such as Scala, Groovy removed the dreaded use of null references to signify the absence of a value.
The similar code can be written in Groovy in a very concise manner. Now we should ask, what a Java developer can do to achieve the similar thing that prevents the possibility of NullPointerException s while maintaining a readable and maintainable source code.
Java language designers chose the similar approach that Groovy or Scala language has already implemented but with the introduction of a new class - Optional. This class is primarily used to signify the absence or presence of a value. If you believe a value can or cannot be present always, it is better to use Optional type.
I have not discussed about the static factory ofNullable.. Just by seeing the API, one could easily understand what needs to be done when an optional type is encountered. For a developer, an encounter with such optional type always signifies the possibility of absence of a value and hence developer can take proper measures for this. From the class overview, we can clearly see that an Optional can be created in variegated ways. So far we have already seen how to create Optional instances.
Now we should see how to extract the value or transform it to another. This is what we mostly do to evade NullPointerException s.
Now with Java 8 Optional , we can write the same as follows:. I used to consider it as an improvement as it hides the null pointers but later on, I felt it pollutes source code quite a bit. But I am not against the use of returning Optional as types from methods or wrapping variables. I will discuss my reasons behind it in the following sections. If we incorporate public String Optional in desiging a good API, this could have been achieved in a more concise way:.
I would strongly suggest to have a quick understanding on Java 8 Streams to understand the beauty of Optional s. Now I would like to share some ideas on designing our previously discussed POJOs in a bit different way.
Here, I have declared the member variable to be of Optional type. According to my opinion, this is also very user-friendly and users or consumers of this class can easily understand the nature of this class. In this context, an employee has a car which is Optional , that is, an employee may or may not have a car as well. This is also quite intuitive but it lacks the idea of clearly showing the absence of a member instance.
To understand any system, developers always require to understand the object model first and understanding an object model requires us to understand the domain objects.
In this scenario, an employee is a domain object that has a car as if it is mandatory for an employee. But in reality, an employee may or may not have a car. We could achieve it when we get or retrieve its value getCar and we could then notice its possibility of the absence of contained value as the method returns Optional.
It solely depends on the developers. I personally prefer the first approach as it is clear in understading the domain model while the second approach has advantages on seralization. If we use DTOs, we can adapt our implementation to the second approach. As I have mentioned previously that Optional in classes clearly shows what the consumers are supposed to do.
So, if a constructor or method accepts Optional element as argument, it means that the argument is not mandatory. On the other hand, we need to pay the price of polluting the codebase with Optional s. I personally prefer not to use Optional in method arguments while if needed we can still wrap it inside Optional instance and perform the necessary operations on it. Java Language Architect Brian Goetz also advices to return Optional in methods if there is a possiblity to return null.
Since years, Java developers follow the usual way to throwing exceptions to signify an erroneous situation in a method invocation. On the other hand, we could also use Optional the following way:.
I think this is very intuitive as it clearly says that it returns an Optional instance that may or may not have a value. Private methods are not clearly meant to understand or analyse any significant part of a project. And hence, I think we still can make use of null checks to get rid of too much Optional s but if you think you still can use the method in a more clean and concise way, you can return Optional as well.
As a first example consider the code you need to implement a method to list files from a specified path in Java. Notice that the return type in the concise method still remains List instead of Optional. It is preferable to follow the usual practice of returning an empty list instead of using Optional.
It is quite patent that the stream ways of using Optional are more concise. Optional is an utility data container that helps developers to get rid of null references.
But Optional can be misused heavily and can pollute the codebase if the developer is not well aware of the primary use of Optional s. Home All Posts About.