19 - Java Collections Framework/004 List implementations - ArrayList, Vector, CopyOnWriteArrayList & Stack_en.srt

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Hello.

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Yes, students, today we are going to talk about implementations of the list interface, we are going

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to discuss such implementations as our list vector question right away, list and stack.

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You have a lot of things to learn in this lesson besides the learning of the specific classes.

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We are going to answer the question when you have to use each particular implementation of list interface.

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I'm going to share with you real life examples where we will use list implementations today during the

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lesson I'm going to show you is a tool that will allow you to investigate the interaction of classes

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in the clips.

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During the lesson, we are going to compare different implementations of the list interface so that

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you could understand what pros and cons of each implementations are in this lesson.

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We are going to compare on the array vector Copan right away and Stack also.

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We're going to learn what mocker interfaces are and what is random access interface.

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So as you can see, we have a huge agenda for today.

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Let's don't waste our time and start our lesson.

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Brunious lessons.

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You already learned what list is, but let's try to answer the question when we have to use list.

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In my opinion, list implementations can cover the requirements of the widest range of business cases.

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Why?

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Because of the next reasons.

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Support of data manipulation by Elements Index.

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You may want to retrieve product from specific index in your list of products, or you may want to put

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user in the list of users in the middle of the list by its index.

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Or probably you always want to add the new user since the beginning of the list, but not at the end.

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The possibility to use index to manage element positions gives you a lot of options for data manipulations

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that will help you in different business cases.

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And another reason list implementations may contain duplicates.

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Sometimes you just need to have container that will store all your products, for example, and you

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don't care about duplicate there.

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You just need to have a list of all products here.

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That's why, which is at least overset sometimes one more reason usability to create subleased.

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This feature is really attractive.

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One for some specific business cases.

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Let me share with you one example from the real life.

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We implemented mobile app for the betting tips in this app.

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We received data from the server.

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We store the data in the list.

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There was such the main type asport prediction data.

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eSport prediction was done for the specific sports event that may happen either today or yesterday or

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tomorrow.

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So developers created sub lists of the sport prediction for yesterday, today and tomorrow.

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We created three lists instead of one by splitting the original one.

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Why we could pass the one list to each widget to draw the list on the UI interface only for specific

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date.

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That's it, by the way.

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Here is the UI of the sports app, Anderson.

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You will be able to create similar apps, so don't worry.

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To implement such application, you have to know implementations of the list interface.

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Let's move further certain.

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And again, one more features a collection interface doesn't have.

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We may sort our button Tepes based on the level of probability that really improves interaction with

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the app.

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Moreover, I can offer user to source support.

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Prediction is a high probability score or by keep also rating or by anything else, wide range of use.

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And one more important reason to opt for these implementations, and this reason probably is the most

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important one that is not written in any book that you read.

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Engineers use list implementations and most of the times because they just don't use a set.

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Documentation's developers just need some container to store multiple elements in there and treat them

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as a single unit without any extra features.

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OK, now we want to know when and why we opt for liste implementations.

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Let's investigate list Iraqi on this slide you may use at least the interface is implemented by absoluteness

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class.

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Absolutely.

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Tintern extends APSA collection and is extended by Absol sequential sequentially.

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From this diagram you may see that our own list is extended directly from the absolute list, the same

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as vector and copy and write and released and linked list is extended from absolute sequential list

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stack class extends vector engineers.

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Doesn't like Stack for that because that is not the least by its essence.

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It is closer to the reverse.

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CU does a deck interface.

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We're going to run it later, but because of the backward compatibility creator subject didn't change

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anything here.

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Is it clear?

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Because Stack in its essence implement last in, first out principle, but it extends least interface,

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but not that.

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Even despite this, glass will not be used very often by a during the development, you might be asked

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about it during the interview.

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That's why I decided to mention it here.

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What is also worth to mention is the implementation of random access interface.

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Today during the demo, I'm going to show you what random access interface is and what mocker interfaces

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are to protect our lesson today as I just jump into the eclipse to investigate the source code that

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will help us to learn the topic better understand them.

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I'd like to share with you the trick that will also help you in the future during the development.

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Namely, I'd like to show you how you can easily find implementations of each interface and reviews

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a whole Iraqian, for example.

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Here is a list interface.

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I should put the cursor into the editor error and press efore button.

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Or you can also make mouse right.

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Click and select open type Iraqi here and we can see that the separate widget is open.

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Here, here I see items that extends or implements the interface.

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For example, here's our list.

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We can make a left mouse click to open it and here we may find our array list.

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As you can see, there are really a lot of classes over here will not run.

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Each of them instead will focus only on those that you will use during your work.

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Let's start from the most popular implementation of this interface that you will use in 98 percent of

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cases.

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That is just my assumption.

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But you will tell me that if I was right, here's a release class when people are released because it's

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really fast and most simple words released is array with dynamic size.

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But this is in very, very simple words.

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I only use regular arrays inside to store elements here.

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This is a variable is called element data in my store array of objects.

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That means that technically we can put everything in this array, but we can't because this field has

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packaged private modifier.

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OK, then you might be wondering if I only use this regular array to store elements, then it should

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have fixed size, is that correct?

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That is correct.

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Arrays in Java have fixed size, but not the array.

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Least let me show is a code that adds element to the collection.

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Here is an element method in today's modification count variable first.

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Don't pay attention to that right now.

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After that it calls another add method.

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I hold control key and press mouse left click.

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OK, here is a private matter and you see the first line we have if statement here we check if s equals

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to the length of the array, then we initialize our element data array with the new array.

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Before we go further, let's look what this s variable is.

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I hold all key and press our left key to move back to the previous position where I was.

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And we see that the argument in this method is a size variable size is also one of the fields in a release

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class.

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Now let's get back.

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I keep all key press and also press arrow right key to get back to the place in the source code where

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I was before.

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Now, you know, that s is a size.

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What does Groom method do?

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Let me answer that question.

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OK.

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This method calls another group method within argument and person size plus one there.

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And what do we have here?

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We see that in arguments that we passed to this method is used to define desired minimum capacity.

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You may see has that old capacity is equal to arrest lengths and in case old capacity is more than zero.

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We calculate new capacity, how it is calculated.

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I suggest you to investigate by itself by going deeper and method and location change.

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By the way, you might see here bitwise shift.

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And it is great that by this lesson you already know how it works.

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If you don't know, please review my lesson from the Java course about operators.

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And after that we use a race class to copy our current theory to the one with the new capacity and we

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return the reference to this array.

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So now you can understand that when there is no space for new element Ansary, the values from the old

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are a cockpit to the new array was the new size.

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OK, but what happens if we have just created the of our type and it's empty?

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Let's check the default constructor.

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We can see that element data is initialized with the empty array.

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This is constant empty array.

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But why do we need this default capacity constant?

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To answer this, let's get back to zero method.

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Pay attention to the if clause here.

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If old capacity more than zero.

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And we know that when our only has been just created, its size is zero.

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And the second clause is if Elliman data is not equal to the full capacity MHRA.

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We know that this statement is also false because we initialized our rate with this constant.

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So that's why our full program execution goes to the else block where we initialize our element data

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array with the rate of the Langston Wighton because it will take Maximilien between ten and one during

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the creation of three.

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Does it make sense now as a part of your homework?

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I would encourage you to go over each method in a release like we did with Add Method to understand

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how Array Works program.

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You might be wondered whether you can create an array list with a specific capacity.

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Yes, you can arrange.

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This has special constructor for that here it why you may need to create array list of different capacity.

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Let me explain.

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You imagine that you created array list with capacity of 10 elements.

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That means when you will add 11 element and after that sextants element and so forth, each time I should

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copies of values from the previous array and add them to the new array that will cause some spikes in

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our performance.

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Then if you know that you're going to add to your rate around one million elements right after creation

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of the array, at least it is better to set capacity at the beginning to avoid some spikes in the performance.

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If we specify capacity for one million elements, we will avoid case when we constantly copying arrays

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and creating new objects of arrays, keeping the old arrays in our memory until garbage collector will

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remove them.

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Is it clear now why you might want to create an array with the initial capacity?

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Great.

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Let's move on.

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There is also one more interesting use case.

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Imagine that you added new elements to your array list and after that you removed nine thousand one

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hundred elements.

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OK, there is a one thousand hundred elements in your list.

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But what its capacity, its capacity is still one million to remove new elements from our array.

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Inside our list we may call stream to size method.

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This method streams the capacity of the relist instance to the list.

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Current size.

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OK, now you know how the dynamic extension happens in Frailest, I also promised you to explain what

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random access is.

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Can you see that array list implements random access?

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Let's take a look at this interface.

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Can you see that this is the empty interface?

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It doesn't declare any contract for any behavior.

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Then why do we need it at all?

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Random access interface is a marker interface.

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Sometimes in you would see so-called marker interfaces.

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Why is called so xcode so?

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Because the only reason why they exist is to mark interface with a specific type to use this information

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in the future.

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Probably it is still not clear for you.

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But let me show you on the example.

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Here is a random access interface which is used to mark any class that supports retrieval of elements

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for the constant amount of time.

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That's actually one of the key features of our list is a constant amount of time for reading an element

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is because of the nature of a release and how it works under the hood.

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To read an element, you just need to get it from array by specific index.

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And this time is usually constant.

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That's why our list is marked as implementation of random access.

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Now let's see where this information is used.

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If we would open collection class, this is class with utility methods nonwar, it will run it in the

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separate question.

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Right now, I just want to show you how information about market interfaces used I press control and

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you simultaneously to search through this file and I want to search for random access words and I have

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around fifty eight mentions.

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You can see that random access is used with instance of operator and if closes to select specific algorithms

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that will work the best here in binary search method.

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You may see that in case that were passed as parameter to the mass that is compatible with random access

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type then indexed binary search algorithm will be applied.

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If no, then iterate a binary search method will be called.

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And similarly, in the other method, check for compatibility with random access interface is used to

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select the best algorithm.

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Right now, I believe you understood the use case and how much the interface may be used.

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That's great.

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According to the agenda.

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Also, we're going to cover today a few more classes.

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Zaya Vector, Cooperton writer released and Stack.

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While covering those, I will be super fast because they are mostly the same as I released, so I would

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draw your attention only to the things that are different from the released here of Extra Vector.

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It is almost the same as it released the same mechanism of storing data.

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Here is the element data array to store elements.

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There's only one big difference between a release and vector on assets and vector a synchronized.

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What does that mean?

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Let's take a look at the ad method.

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For example.

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Can you see the key words synchronized in the method definition?

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We didn't learn yet this keyword in detail, but we will we will run it in the details durians and we'll

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just write in top it.

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But right now you can understand this keyword as a restriction for multiple threats of execution and

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the method, but body simultaneously.

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That means if two threats of execution want to add element, remove element or replace element of a

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specific index, they won't be able to do this simultaneously.

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All these operations will be performed one after another.

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That would save you from the data inconsistency inside the vector.

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That's why Vector is called safe container.

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Does it make sense?

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OK, let's go further.

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Let me open a copy right away.

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List the same stories here.

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Right.

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Or at least is a safe version of the array list.

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Then what is the difference between vector and copywriter?

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At least Corporan.

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Right.

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The list was introduced in Java version five.

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Well, Vector was introduced in the version first in version five.

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Engineers come up with improvements in performance for this, let's say, version of a release.

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And we can say that right writer released is more efficient from the performance standpoint.

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In comparison with Vector, for example, let me open add method.

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Can you see this?

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There is no synchronized word here, but synchronized block instead.

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The White House improvisation is implemented in this class is different from the way it is implemented

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in Vector.

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That is the difference between vector unreleased and Copan.

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Right?

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Frailest.

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And now let's open this attack was, as you remember from the beginning of the lesson, Stack extends

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factor.

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But take a look at the map that introduced instead.

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What does this remind you of your right that is almost interface of the cube.

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The names of the masses are almost the same.

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Engineers don't like Stack because this is concrete glass.

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That means there is no flexibility in using different implementation of the same API.

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It implements LIFO principle.

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Last in, first out.

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We are going to review this principle in the details when we get closer to the interface.

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So don't worry.

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Years for now, the LIFO principle is implemented in DEC interface and in different implementation of

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that interface.

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But Stack was introduced in Java version one and keep the promise of backwards compatibility and to

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make sure that programs that are written on Java version first will be successfully executed on the

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Java version fifteens.

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And later this class is still here.

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That's it.

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Now, you know, also the difference between a release vector, right.

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And released instead.

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Now let's recap what we have learned today.

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Today, we investigated the Iraqi of least interface.

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You saw how you may investigate source code and you Iraqi of any interface in eclipse.

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Also in this lesson, we learned when we have to use implementation of the interface, such as every

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vector writer relist, and so that we learned in detail how size of the array maybe dynamically increased

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in there.

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At least now you know the difference between a real E vector right at released and stack.

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During the lesson we learned what Mark interfaces are.

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On the example of random access interface, we learned how market interface might be used.

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That's what we have for today.

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