Sets are another type of data structure that do not preserve order.

Unlike tuples, sets do not allow duplicates.

Each element's order is determined by the value returned from the hash code method.

Sets are immutable by default.

Let's start by cleaning up some of our previous code associated to maps

and tuples.

Awesome, let's create a set of integers from one to five.

In this example, we insert each value in the set in increasing order.

However, if we print out the values of the set,

the first thing we'll notice is that the order is not preserved.

Let's take a look.

Let's recompile and check out our results.

If we really want to maintain the order that each element was inserted in the set,

we can use a LinkedHashSet, which implements a linked list under the hood.

To do so, we will need to import the scala.collection.mutable LinkedHashSet.

Let's do so at the top of our file and create a new LinkedHashSet.

Awesome, let's recompile our app and check out our results.

Perfect, we've created an orderedSet that maintains the order of our elements.

In order to create a mutable set,

we need to import the scala.collection.mutable set.

Let's do so at the top of our file and create a new mutable set.

Similarly to other collections to add or remove elements from a set,

we would simply use the plus equal or minus equal methods.

Let's take a look.

Great, let's recompile and check out our results.

Awesome, as expected, we were able to remove the number 5 from our set, and

we're also able to add the number 4.

We can achieve some very useful functionality with sets, and

that's by using the methods intersect and union.

Intersect grabs the values which are contained in both sets,

while union adds each unique value in both sets.

Let's take a look at how those work.

Awesome, as we can see, we have a set for

the unionResult and a set for the intersectResult.

Let's dissect the intersectResult.

Remember, intersect just means that we grab the values that are contained in both

sets and here, we get the number 4.

That's because both sets, nums as well as numbers, both contain the number 4.

Great, we've gone through quite a few collections in Scala, and

we've learned a lot about Scala's mutable and immutable data structures.

In the next videos, we'll learn about high order functions in Scala, and

how to apply some of those functions to Scala collections.