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Hello.

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Students in this region, I'm going to make overview of Java collections framework.

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I want you to understand general structure of Java collections framework before we start going deeper

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in the details.

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And here's our agenda for the day.

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We'll talk about what GSF includes in this lesson.

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You are going to learn the difference between collections and the rates.

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We are going to discuss what advantages collections have over their rates.

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Also, during the lesson, we are going to talk about two separate Iraqis in Java collections framework

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that Zeta's Iraqi of collections and hierarchy of maps.

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And what are the difference between them?

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I believe this is going to help you significantly to understand the core structure and the next lessons

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in general.

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So let's start and to start with let's answer the question.

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What does you see, if I will shut and Java collections framework, if you don't mind.

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What does it consist of?

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GCF is a unified name for the group of the types and algorithms that are developed to store elements

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in them and perform manipulations on the group of the objects.

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GCF includes next things, collection interfaces.

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These are abstract data types that describes the type that my group, multiple elements in the single

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unit as a software engineer, are going to use collections all the times to perform operations with

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the group of objects, for example, product list in our Web application.

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This might be a collection of products in the language of Java, and we could perform operations on

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the group of the products, for example, search products, or filter them to keep only products that

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has priced more than ten dollars or split all the group of products on the equal chance to show products

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page by page and a lot of other things.

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Can you understand now why we might need collections?

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You might think.

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Isn't that the same what we have arrays for take into account you used to raise already?

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You might think that for the same purposes you would use arrays a bit later when we would talk about

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advantages of collections of arrays.

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You would understand why arrays and collections are two different things implementations of collection

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interfaces, even despite the fact that abstractions for collections looks the same, the implementation

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of this interface at different and fits for different goals.

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For example, some collections work the best for adding new elements since the end of the collection,

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and developers like that collections because of the constant time of retrieving element from them.

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Are the collections work better when you need to add elements in the middle or at the beginning of the

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collection?

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Other collections work the best in the current environment.

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We are going to learn all of these collections and to understand the difference when to use each collection

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type.

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Map interfaces, map interface at different from collections in one important think map is a container

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that contains pairs of key and value.

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For example, you may the name of the product category, for example, doors and collections of all

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doors associated with it.

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You might have goods category and collection of booths associated with that key.

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And in case you need to get all doors, you just make a request to the map button on the key to it to

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retrieve all doors.

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Does it make sense?

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Maps are also considered a part of the collections framework because even if they don't have the same

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interface as collections, they have operations that allow us to view and interact with them the same

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way as with collections.

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Implementation of MAP interfaces unions, of course, we are going to discuss different implementations

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of the map and we are going to understand when we will use each implementation of the map interface.

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Deprecated collections, deprecated collections are also part of the Java collections framework, despite

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the fact that it is recommended not to use specific collections sometimes on the Java project.

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You still going to work with them?

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Because even nowadays there are a lot of old projects written on Java that require support and maintenance,

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synchronized collections.

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There are also special set of collections that are developed to be used in the multithreaded environment.

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Let me tell you the example to make you understand.

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Imagine that you have collections of users and one administrator of the website removes the user from

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the collection and another administrator of the website is iterating over each user in the same collection

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to update the state of the total.

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Orders about the conflict might appear when two administrators in the two separate threats of execution

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would obtain the same collection.

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In this course, I'm going to tell you how centralized collections work and how to use them.

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Algorithms also.

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GCF includes algorithms that are the methods that perform useful computations, such as searching and

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sorting on objects that implement collection interfaces that algorithms are said to be polymorphic.

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That is, the same method can be used on many different implementations of the appropriate collection

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interface.

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Robbers GCF contains a special wrapper that can turn your regular collection into non modifiable collection

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or wrapper, that can turn your regular collection into synchronized collection that you can use and

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will just write an environment.

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Now, when you know what a collection framework consists of, let's discuss what advantages does it

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have over race?

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Let's go over this table to compare collections and race.

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This table will help you to understand what advantage collections have over race.

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First of all, you already know that our racing driver have fixed size collections in Java can be extended

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dynamically.

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So using collections, there is no need to create new collection and copy the state of the previous

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collection into the new one when you run out of space in this old collection.

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There's a significant benefit for the development process.

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Secondly, our race itself does not have any behavior and algorithms to work with them, for example,

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a race can't filter themselves or find the first index of appearance of element or keep all elements

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sorted automatically or have only unique elements and do not add elements that already exist in collection

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and a lot of other things.

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If you remember a race class, you may say that some of the algorithms are present in a race class to

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work with the race.

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But the amount of operations that you can do with our race class is significantly lower than a number

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of algorithms that Java collections framework has.

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And moreover, we mentioned separate class and static methods in a race class that is not the same as

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behavior of the object like we have in collections.

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Certainly collections have single API and no matter what is the specifics of each particular implementation

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of the collection, whether it's stauss only unique elements or supports region of elements during the

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constant amount of time, it doesn't matter.

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All collections have common API.

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What significantly simplifies usage of collections and running them.

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On the other hand, working with arrays e.g. developer may implement his own application programming

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interface to interact with a rate.

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For example, the developer may come up with a method to add a new element in array and extend it in

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case there is no more Plaisance.

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Every developer may come up with a specific algorithm.

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How to clear all elements in array.

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One developer will just create a new array with the default array size and as a developer would just

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turn into new values or current elements in array and the already might use a problem and such approach.

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There is no single API when you are working with arrays.

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By having such data structures and algorithms as collections, developers may concentrate on the important

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parts of the program rather than on the low level work and inventions of your.

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Forcedly, what you need to remember, collections can store only reference types of data collections

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doesn't work with primitive types of data.

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If you want to store primitive types of data because of the performance reasons, you still have to

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use arrays.

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And last but not the least performance.

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Usually it is considered the performance of arrays is higher than performance of collections.

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While this can be true in the modern world, in the most of business cases we are talking about milliseconds

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difference for standard operations and for standard number of elements in either collection or array.

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But you have to know about this and now you have the vision of what we are going to learn and what Java

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collections framework is.

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As you can see, there are really a lot of things to learn.

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Right now, let's recap what we have learned today.

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In this lesson, we learned what Java collections framework contains on the high level.

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We understand what collections are and how they are different from maps during the last very of the

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main advantages of collections of arrays and also discussed what advantages arrays have over collections.

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That's all for now.

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