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This article focuses on "how to use collections in Scala". Interested friends may wish to have a look at it. The method introduced in this paper is simple, fast and practical. Let's let the editor learn how to use collections in Scala.

One of the core features of functional programming is to pass the function as a parameter to the function, and the function can be defined inside the function.

1, hands-on Scala higher-order function

Declare an instance of the List collection:

The package in which the List collection is located has been predefined and automatically imported, so there is no need to import the package here. At the same time, the List instantiation object is directly used here, which is actually the apply method of the object object of List.

We use the map function to multiply each value in List by 2:

In the above code, x represents each element in l, and map traverses each element in l. Since there is only one type of element in List, we can omit its type when performing the map operation, as shown below:

When there is only one parameter in the List collection, we can remove the parentheses from the parameter:

In the case of only one parameter, the more concise and normal writing is as follows:

The commonly used high-order functions are map, filter, reduce, and so on, which we will introduce later.

2, the collection in the hands-on Scala

The collection mainly includes List, Set, Tuple, Map and so on. Let's learn it in a hands-on way.

Let's create an instance of List in the IDE of Eclipse:

At this point, let's look at its code implementation:

It is explained in the source code that it is instantiated in apply.

In the same way, we can instantiate Set:

At this point, you can also take a look at the implementation of Set instantiated objects:

Next, let's take a look at the operation of the collection in the command line terminal, first take a look at Set:

You can find that there are no duplicate elements in the Set.

Take a look at the declaration and use of Tuple:

From the above code, you can see that the subscript starts at 1 when the source code is accessed.

For Tuple, if there are only two elements, you can also create it in the following ways:

Let's take a look at the definition of Map:

Map itself uses variable arguments, so you can assign multiple values to Map:

Let's take a look at the Option type, where Option represents an optional value:

Option has two subclasses: Some and None. Let's take a look at the use of Option:

Next, let's take a look at the processing of filter:

Let's take a look at the zip operation on the collection:

Let's take a look at partition's cutting operation on the collection:

We can use multiple collections of flatten for flattening:

FlatMap is a combination of map and flatten operations. The map operation is followed by the flatten operation:

At this point, I believe you have a deeper understanding of "how collections in Scala are used". You might as well do it in practice. Here is the website, more related content can enter the relevant channels to inquire, follow us, continue to learn!

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