19 - Java Collections Framework/018 SortedMap, NavigableMap & TreeMap_en.srt

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Hello, adjustments in this lesson, we're going to learn another implementation of map interface,

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let us dream that we are going to learn in detail such interfaces as sort of map and navigable map.

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This would help us a lot in understanding of dreama behavior.

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And at the end of the lesson, we'll have practice with three map and I'll show you how you can use

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this map with keys that are implements comparable interface and with keys that don't implement comparable

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interface.

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We are going to learn what the minority is, what red black minority is and why big ol notational three

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map for its major operations is all of luck.

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And let's start and to start with, I'd like to jump to the source code of the sort of map interface

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to investigate what message I introduce that here is the source code of sorts of map interface.

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It extends map interface.

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As you can see here, the first method here in our list is compared to this message of return comparatives

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that is used in map to source keys or now if such comparator is absent and MAP uses natural ordering

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of keys.

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To be honest, this method was not used by me and I think it is not very popular because if you use

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some comparator to source keys in the map, that means you have the reference to this computer already

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somewhere in your program and there is no need to get it from the map.

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And in keys are sorted according to natural order.

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And there is no sense to call this method because now will be returned.

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But now you at least known about this method and can use it someday in the future when this will be

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named.

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The next method here is some map.

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I would even say that it is similar to subleased from Liste interface.

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The principle applied is the same here.

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We have to specify a key from inclusively and key to exclusively and we will get new sorted map in response.

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It is also worth to mention that the majority of methods and so that map potentially Mistral class cost

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exception in the case keys can't be cost to comparable interface or in case there is no comparison available

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in this map.

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Besides, with exceptions, there are also a few more potential exceptions that are pretty straightforward.

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Not pass now as Massata argument.

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In case you don't want to catch Northpoint exception and do not pass from Ki's that is greater than

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Tukey to not get a legal argument exception.

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The next method is HapMap.

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It returns the view of the map that is less than key given.

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For example, if you to retrieve all entries at the last and some specific key you can use.

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This method to map works in the opposite way.

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It returns the view of the map that contains entries with keys that are greater than or equal to the

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keys that will be passed as method argument here also.

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So that map provides the massive that allows us to access first and Laskey.

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That in turn will allow us to retrieve value from map by this key.

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That's why we have first massive that returns the lowest key.

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And Laskey, Massachusetts returns the highest key key said the method similar to the one we have in

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our map interface.

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But with clarifications to its implementation, the set that will be returned has iterator that returns

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the keys in ascending order.

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Well, this method returns collections.

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That has iterator, that returns the values in ascending order of the corresponding case and last method

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here that is also familiar to you.

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That is entry, said Estrogen's entries in ascending key order that's so massive that introduced and

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studied map interface.

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Let's move further and look at the popular interface that extends the solid map interface.

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I'm talking about navigable map.

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Here is the source code of navigable map interface.

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Let's look through the massive data declared here and I will give my comments.

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The main feature of this map is that it returns the closest matches for given search Target's main message

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that they introduced in this interface and created to reach this goal.

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For example, here's the first matter now at least lower entry.

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It returns an entry that is key value mapping associated with the greatest key that is strictly less

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than the given key.

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I'm going to show you this massive difference, the demo in a few minutes to make you understand how

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this method works.

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On example, lower key, Masset returns not entry, but on the key.

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It returns the greatest keys that is typically less than the given.

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Key to next method is floor entry.

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It is different from low entry because it returns key value mapping associated with the greatest key.

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That is not strictly less of the key, but is a less than or equal to the given keys that will be passed

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as method argument for key regions.

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Not entry, but only key according to the logic that we have just discussed.

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Celan entry regions entry associated with the Leskie greater than or equal to the given key.

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I always do analogy for myself with the real ceiling in my house to remember the logic for this matter.

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So this message should return the.

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That is right on my ceiling or above it, but not the element from the next floor.

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That's why it is set about liste entry greater than or equal to the given key.

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Does it make more sense now?

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Holmes's understanding will help you the same as it helps me see key returns key according to the ceiling

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logic that we have just talked about, the next Masad higher entry written entry with the key that is

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strictly greater than the given key.

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In this particular case, I always want to get aliment from the next floor, the disclosers and other

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elements to my ceiling.

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This this example, in case we want to continue a real life analogy with the house that we started during

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the learning of previous Masset hierarchy.

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I believe you already understood the way how these methods are structured here.

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Also, navigable map will provide you fast access to the first entry in the map.

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That is the answer was at least key to yet it just called for a center method and also access will be

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provided to the last element in the tree to get it.

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Jesco last entry here you can find a method similar to those that you saw in Q and DEC interfaces.

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We can get and remove first entry from the map for that pole.

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First entry.

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MassArt exists and we can get and remove last entry from the map by Colin Powell.

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Last entry, take into account the navigable map is sorted map.

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We also can get navigable map in reverse order.

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We have to call Distending Map.

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In this case we also can get navigable set and the standard set by the method name and believe it is

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clear that order of keys in the he said is reversed.

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He said life message that we also saw in sort of map, but it works with additional MassArt parameters.

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In this case, developer can specify whether we want from key inclusively or not the same as we stookey

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that the level of flexibility that is added in addition to some map from sorted map interface.

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We also have had map and tail map massas declared in this interface with only one difference that we

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can specify boolean flag to include or exclude the key from the result.

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And the last three matters here are equivalent to the ones that are declared in solid map interface.

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Now it is time to practice a bit.

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And for the sake of the demo, I prepared the file with examples.

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I will also share it with you so that you could practice and run the code on your computer.

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Let me run the program and walk you through the console output here and declare the variable of navigable

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map type and initialize it with three map object, three map extents, observe map and implements navigable

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map.

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It is considered as the most popular implementation of navigable and sorted map interfaces.

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For the sake of the demo.

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I just put integers and strings into this map like this.

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And here you can see different examples of me using the first entry, lower entry, floor entry, higher

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entry and Celan entry methods.

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I used three as a key for all Magidson and locations so that you could see the difference here.

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You can see that even despite the order in which we put entries when we retrieve first entry, we got

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one because integer object implements comparable interface and integer objects know how to compare themselves

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with the other integers.

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Does it make sense now?

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When I call lower entry, I receive two because the condition for this method is that entry with the

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greatest key that is strictly less will be returned.

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But when I call floor entry for keys three, I receive entry with the key three because condition is

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different and it allows the key would be equal to the one even as method argument.

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Similar story with higher entry and Celan entry, but in another direction here, a printed map and

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you can see that it is ordered.

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I can easily get map in descending order by calling the standing map method.

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And here you can see in console's at all entries assaulted in the reverse order.

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Now the thing that you should remember is that we will throw class cost exception in case you would

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put objects that don't implement comparable interface.

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But what to do in such cases?

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We have to pass comparator to the three map constructor that is going to be used to compare keys inside

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here I created one more map where our keys will be of type products that we used for our online store

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creation and our values would be of type user.

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But the type of the value does not make a big difference since Shorten is performed by keys.

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And here you can see that I created object of comparison that we implemented during one of our homeworks

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and put this object in constructor here.

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Now I add few entries here and when I printed to console each key from you, I you can see that all

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of them are sorted in order that is defined by our comparator.

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That's why three map is often used to sort map by its case.

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That said, regarding examples of how you can use to map the next things that I'd like to talk about

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is performance of three map and how Swardson is implemented in this container.

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The first thing that is worth to mention is that we map is not based on hash table.

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It is based on red, black, self balanced binary tree.

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That's why complexity of algorithms for main operations like get put remove is a big O of logarithm

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at the dive into the details and explain what an algorithm is I and to try to explain it in these words.

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The performance is not linear.

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That means it doesn't depend on a number of elements in the map in one to one proportion.

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But performance is Calan as we have more elements to visualize this in your head.

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Take a look at this slide.

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You can see the visualization of mapping between number of elements and times that it takes for specific

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operations mapped to the connotation.

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You also can find the core of the algorithm and on the picture how this makes things clearer.

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How is this achieved because of the red black self balance binary tree.

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Let's learn.

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What is it?

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Let me start from explaining what a binary tree is in simple words.

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This is such an algorithm that consists of the nodes or leaves that source links to notes that are greater

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on the right and notes that are less on the left.

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This tree has the root and that's why we can say that all elements that are greater than the root are

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stored on the right and all elements that are less than the root are stored on the left.

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That's why when I need to find a specific element, I don't iterate over all elements.

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I go only to show this past.

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I have to go to find the elements that I need.

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One potential problem you can see in binary tree.

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The problem is.

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Defines the root of the tree in case will define the root and all foreign elements will be greater than

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the root and will be placed on the right.

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Then I will get linked list and performance of main operations will be worse than in binary three and

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will be linear.

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What to do in this case, it might be a good idea to recalculate the root of the tree on regular basis,

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to have the same or almost the same number of elements on the right and on the left side of the root.

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That the moment when red black tree comes into the game, each node stores an extra to and caller used

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to ensure that the tree remains approximately balanced urine insertions or deletions.

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That also ensures because of the algorithm and complexity for main operations with red black tree tracking,

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the color of each node requires only one bit of information overload because there are only two colors.

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Does it make sense now?

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You know how sordidness performed into map and how it works inside.

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That's all what I wanted to share with you.

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Let's recap what we have learned today.

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Labellers sorted map interface and navigable map interface.

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Now, you know, nattered that are declared in these interfaces.

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Also we had the practice Westry map and now you know how you can use it.

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We learned what a binary tree is and what a red black binary tree is.

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Now, you know why performance of major operations of tree map has logarithmic connotation.

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That's it for today.

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Thanks a lot for your attention and see you in the next lesson.