Maps and Tuples

Hi, in this video we'll learn how to implement maps and tuples in Scala. 0:00 Maps or hash tables are collections of key value pairs. 0:05 Tuples, on the other hand, are an immutable sequence of values. 0:10 They are also quite useful for aggregating values. 0:13 Let's get a better idea on these topics by implementing some examples. 0:17 Similar to previous videos, Scala collections can be mutable or immutable. 0:22 By default, when we construct the map in Scala it'll be immutable. 0:27 Let's see how that works syntactically. 0:32 First, let's clean up our superheros object and 0:35 remove anything associated to lists or list buffers. 0:38 Awesome. 1:14 We have created a map of type string and 1:14 integer with the superhero name and ranking. 1:17 Next, let's see how we can access values in our map. 1:21 Similar to Java, except without using the get keyword, 1:34 we look up values in a map using parenthesis and passing in the key. 1:37 And in this case we'll return a ranking of ten. 1:42 You may have noticed that the key is case sensitive, and 1:45 it is possible that the key we are looking for is either misspelled or doesn't exist. 1:49 For instance. 1:54 This will throw a no such element exception because the key is now found and 2:03 it'll crash our program. 2:07 Let's recompile and run our app. 2:10 As expected, we get a no such element exception that crashes our app. 2:13 It is considered good practice to use a method called getOrElse, 2:18 which will return the value if the map contains the key. 2:22 Otherwise, it will return a default value. 2:26 Let's take a look. 2:28 In this example, the code will either return the value of the key, 2:39 ironMan, or zero if it is not found. 2:44 But now our program is safe from the key not found exception and won't crash. 2:46 Additionally, we can retrieve out the keys and 2:51 values over our map using .keys and .values respectively. 2:56 Awesome, as we can see, the .keys method returns a set which is a collection that 3:13 we'll discuss in the next video. 3:18 Meanwhile, the .values returns a map-like collection with the values of our keys. 3:20 Great, we learned how to create HashMaps, let's take a look at how to traverse them. 3:26 The following loop construct allows us to iterate 3:31 over all the key value pairs in the map. 3:34 Lets print out the key value pairs of our Avengers map. 3:37 Great, if we're only interested in the values, 3:58 we can loop through avengers.values. 4:01 Let's recompile and run our app. 4:14 Awesome, so far we've only implemented the mutable map. 4:17 Let's construct a mutable map and see how we can use it to update values and 4:22 extend our map. 4:26 Let's import the scala.collections package at the top of our file and 4:28 create a mutable map. 4:34 Awesome, this creates a mutable map of type string and integer. 5:13 Now we can update the contents of the map. 5:18 Let's up Iron Man's ranking as Tony Stark's new invention makes him much, 5:20 much stronger. 5:25 Now we can also add a key value pair to a map using the += method 5:35 Additionally, to remove an element we can use the -= method and 5:49 pass the key of the element we would like to remove. 5:53 Let's take a look. 5:57 Great, let's comment out some of our previous print line statements and 6:04 recompile our app. 6:08 As expected, we've changed the ranking on Iron Man, we've added Hawkeye, and 6:32 we also removed Captain America from our map. 6:37 Awesome, we now have a really good understanding of how maps work. 6:41 In Scala, 6:45 tuples are very easily created by providing values enclosed in parentheses. 6:46 Let's switch back into our code and create some tuples. 6:51 In this example, we've created a tuple three instance with the types string, 7:15 string, and char. 7:19 Tuples in Scala are actually classes that contain a collection of elements. 7:21 Scala only supports up to tuple 22. 7:26 Which means that we can only have up to 22 elements in a tuple. 7:29 Unlike some of the other collections we saw, tuples are not zero index space, but 7:34 rather they start at one. 7:38 Accessing the first element in a tuple can be done 7:40 with an underscore followed by the index value. 7:43 Let's take a look. 7:46 Let's recompile and run our app. 8:11 Awesome, we were able to retrieve Hawkeye's name and also his birthplace. 8:18 To loop through the elements in a tuple, 8:23 we have to use a method called product iterator. 8:25 Great, let's recompile our app and check out our results. 8:39 As expected, we've printed out the name, birthplace and gender of Hawkeye. 8:44 Awesome, we learned what maps and tuples are and how to perform operations on them. 8:50 In the next video, we will learn about another data structure called sets. 8:55 See you there. 9:00