New optional string
- Optional String, Integer: Named Arguments - Dot Net
- .net - C# - How to Handle Optional String Parameters
- Some ways to initialize Optional object in Java - Huong
So, there are solutions to avoid using Optional s as method parameters. The intent of Java when releasing Optional was to use it as a return type , thus indicating that a method could return an empty value. As a matter of fact, the practice of using Optional as a method parameter is even discouraged by some code inspectors.
Optional String, Integer: Named Arguments - Dot Net
The getMyDefault() method is called in each case. It so happens that when the wrapped value is not present, then both orElse() and orElseGet() work exactly the same way.
.net - C# - How to Handle Optional String Parameters
Note that we used the isPresent() method to check if there is a value inside the Optional object. A value is present only if we have created Optional with a non- null value. We'll look at the isPresent() method in the next section.
Some ways to initialize Optional object in Java - Huong
In the previous tutorial , I introduced with you all about the Optional object in Java. In this tutorial, let 8767 s find out some ways to initialize your Optional object in Java.
The orElse() method is used to retrieve the value wrapped inside an Optional instance. It takes one parameter which acts as a default value. The orElse() method returns the wrapped value if it's present and its argument otherwise:
Let's assume we want to check the correctness of a password input by a user we can clean the password using a map transformation and check it's correctness using a filter :
In the previous section, we looked at how to reject or accept a value based on a filter. We can use a similar syntax to transform the Optional value with the map() method:
The orElseGet() method is similar to orElse(). However, instead of taking a value to return if the Optional value is not present, it takes a supplier functional interface which is invoked and returns the value of the invocation:
You should never ever put an Optional (neither a Stream) in a Class. Those are not serializable and this is by design. Optional should only be returned from a method. It is here to control the flow of execution, not as a storage class.
Additionally, using Optional in a serializable class will result in a NotSerializableException . Our article Java Optional as Return Type further addresses the issues with serialization.
While using map() method, therefore, we need to add an extra call to retrieve the value before using the transformed value. This way, the Optional wrapper will be removed. This operation is performed implicitly when using flatMap.
This is the major flaw of the get() method. Ideally, Optional should help us to avoid such unforeseen exceptions. Therefore, this approach works against the objectives of Optional and will probably be deprecated in a future release.
In the above example, we wrap a null text inside an Optional object and we attempt to get the wrapped value using each of the two approaches. The side effect is as below:
If you are willing to play lose and treat null, "", and whitespace characters to be the same, then you can default to null. This becomes very handy when user name and password are optional fields due to a possibility of trusted connection to a db. You could change this logic to reset strings to null and thus modify the assert and the if. The important part is having a consistent convention.
The orElseThrow() method follows from orElse() and orElseGet() and adds a new approach for handling an absent value. Instead of returning a default value when the wrapped value is not present, it throws an exception:
Here we can observe that how clean our getMobileScreenWidth() API without null checks and boiler plate code. We don not worry about NullPointerExceptions at run-time.
Here if we observe getMobileScreenWidth() method, it has lot of boiler plate code with lots null checks. Before Java 8, we should do all these non-sense stuff to avoid Runtime NullPointerExceptions.
Imagine we have a list of Person and we want a method to search through that list for people having a given name. Also, we would like that method to match entries with at least a certain age, if it's specified. With this parameter being optional, we come with this method:
Just like the map() method, we also have the flatMap() method as an alternative for transforming values. The difference is that map transforms values only when they are unwrapped whereas flatMap takes a wrapped value and unwraps it before transforming it.