Lists | Collections In Scala

Introduction to Lists

In Scala, a List is a collection that holds a sequence of elements. Lists are immutable, meaning that once they are created, their contents cannot be changed. Lists are a fundamental data structure in Scala and are used commonly to store sequential data.

Creating Lists

Lists in Scala can be created using the List companion object. You can create a list of any type, such as integers, strings, or custom objects. Here are some examples:

val numbers = List(1, 2, 3, 4, 5)

val fruits = List("apple", "banana", "grape")

The above code creates a list of integers and a list of strings.

Accessing Elements

You can access elements in a list using their index. Note that the index is zero-based. Here’s how you can access elements:

val firstFruit = fruits(0) // "apple"

val secondNumber = numbers(1) // 2

The first element of the list is accessed using index 0.

Common List Operations

Scala provides a rich set of operations to work with lists. Here are some common operations:

Adding Elements: You can add elements to a list using the :+ operator or the :: operator.

val newList = numbers :+ 6 // List(1, 2, 3, 4, 5, 6)

val anotherList = 0 :: numbers // List(0, 1, 2, 3, 4, 5)

Removing Elements: You can remove elements using the filter method or the drop method.

val filteredList = numbers.filter(_ != 3) // List(1, 2, 4, 5)

Concatenating Lists: You can concatenate two lists using the ++ operator.

val combinedList = numbers ++ List(6, 7) // List(1, 2, 3, 4, 5, 6, 7)

Iterating Over Lists

You can iterate over a list using a for loop or the foreach method:

for (number <- numbers) println(number)

fruits.foreach(fruit => println(fruit))

Both of the above will print each element in the respective lists.

Transforming Lists

Lists can be transformed using methods like map and flatMap. The map function applies a given function to each element of the list:

val doubledNumbers = numbers.map(_ * 2) // List(2, 4, 6, 8, 10)

The flatMap function can be used to flatten lists after applying a function that returns a list:

val nestedList = List(List(1, 2), List(3, 4))

val flatList = nestedList.flatMap(x => x) // List(1, 2, 3, 4)

Conclusion

Lists in Scala are a powerful and flexible data structure for storing sequences of elements. This tutorial has covered the basics of creating, accessing, and manipulating lists in Scala. With this knowledge, you can effectively use lists to handle collections of data in your Scala applications.

Scala Lists Tutorial