Скачать или смотреть Java Optional Example 1

Welcome. Today we are taking an introductory look at the Java Optional Class. We will focus primarily on the Optional Class and what it is for. Then we will cover why it is useful and how to use it in our code. Finally, we wrap up with four hands examples of using the different types of Optional methods in our code.

What is Java the Optional Class?

The optional class is essentially a container object, which may or may not contain a non-nullable value.

Why should we use the Java Optional Class?

One of the biggest problems with Java is that when we create variables or methods with return types, our intent is unclear if the value of these will be null.

String name;
String getName();

void doSomething(){
assertThat("My Name").isEqualTo(getName());
}
He is a simple example where we have a string name, a method that returns a string getName(), and then some method that tries to compare a string name equal to our getName(). The problem with this is name could be null and throw a NullPointerException at runtime. However, just reading the code, we don't know, for instance, if the name was ever instantiated or populated so it could contain a null value.

The code is very unclear on the intent of the name. Should it always be populated, or could the name be null? How, as developers, do we know the name could be null? We don't because the name is just specified as a name.

Unfortunately, this approach leaves it up to the developer to determine the intent of the variable if it can be null. This leads the developer to implement many null checks within their code.

if (name != null) { then do something... }
Primarily what do we do if the name is not known? What do we want to do with it? If we don't know that name could be null, then when we try to use it, we will get a runtime exception all over the place when we try to use the name. This is where Optional comes in.

Why Is Java Optional useful?

When we use the optional class, we imply our intent that a variable or our method could potentially return a no result or a null. Because the Optional class gives us the ability to wrap our variables and methods. Telling the developer that this variable is optional and that name might not have a value in a particular instance; therefore, the variable will not return a value.

Additionally, the Optional class has some methods that handle how we do null pointers or null checks. Same with methods, like our Optional String getName. So this time, in the above code, we create a new Optional String for both the variable and method getName.

By doing this, we are specifying that name may return no result so that it could be null, but because we're using Optional, we will know that we need to handle that case.