WEBVTT

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Hi everyone.

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Welcome back to this tutorial.

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In this tutorial, I'll be explaining about the factory methods that are part of the Steam API.

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The factory methods are of generate and iterate.

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Let's go ahead and take a look at the off function first.

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So our function is used to create a stream of certain values passed to this method.

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Let's take a look at the example.

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So in this example we have the stream, which has a static method called off, which takes certain values.

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In this case it is, it is taking a string.

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Adam, Dan and Julie, this is going to give you a stream of string as an output.

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So we have seen examples of creating a stream out of the list.

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This is one another approach of creating a stream using the off method.

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Iterate and generate are used to create infinite streams.

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So let's take a look at the example of iterate first.

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So streams dot iterate.

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Again, this is a static method.

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This is the initial value, which takes two arguments actually.

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The first argument represents the initial value.

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The second argument is going to give you.

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So in this example, it is going to start from one and it is going to iterate infinite times.

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And every time this method is executed is going to give you the value as one into two, two into two,

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three into two as an output.

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Let's take a look at the generate example here.

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The generate basically takes in a supplier.

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We all know supplier by now, supplier doesn't take any input, but it is going to return you an output.

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Let's go ahead and code this one and then explore all these methods.

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Ardently open what I'm going to do.

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I'm going to create an example.

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Called Stream.

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Of generate.

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It rate example.

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And let me make this class executable by adding the public static void main method.

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Put this in presentation mode.

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The first purpose.

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We are going to create the stream using the off method stream dot off method.

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As you see here, I have this off method.

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I'm going to pass in values like Adam, Dan.

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Julie.

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That's it.

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So this is going to return a stream of string as an output.

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And then I'm going to name this one as string stream.

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So let's go to this off method.

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Go.

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If you take a look at the off method, it takes an infinite number of values and then it is going to

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return a stream of type string.

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So whatever type that you're passing, that is a type that it is going to return.

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So what we will do, we will just iterate.

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The for you for each method.

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System.out.println.

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Run this example that is going to print all the values in the console.

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There you go.

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It printed the Adam, Dan, Julie.

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This is one way of creating a stream of the values that you can pass as an input to this off method.

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Now let's explore the iterate method.

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I'm going to type in the stream class dot and then we are going to make use of the iterate method.

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We go to the iterate method.

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Iterate method takes in two input.

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One is the seed, which is the initial value, and then the unary operator, the unary operator.

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We all know by now it is going to take an input of one type and then it is going to return the output

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of the same type.

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So I'm going to have the initial value as one, and then I want to perform a multiplication of two for

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each value that it is going to return.

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And then I'm going to do for each it's going to be system dot out, dot println.

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I want to print and then show you how the values look like first and then we'll explore some additional

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enhancements for this particular iterate method.

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Now run this.

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I'm going to stop this one.

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So here it is, printing zero.

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Let's go to the top of the console and then take a look at what's happening there.

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So it printed Adam, Dan, Julie.

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That's what we are doing here.

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And then if you take a look at it, it printed the initial value and the following value is the multiplication

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of that initial value into two, followed by that the previous value into two, the previous value into

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two.

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It continues until it reaches the max value of an integer.

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So here, this is an integer, right?

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So it reaches this max value and after that it is just printing zero.

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The reason why this is happening is because we are iterating in finite times.

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So there is a handy function which is part of the Stream API which we covered in one of the previous

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tutorial.

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You can use the limit to limit the number of values it can pick from the stream and then perform this

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iteration.

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So in here I'm going to have the value as ten.

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Basically, this is going to limit this iterate to just pass ten values and then it's going to stop

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the infinite stream.

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If I run this example that is just going to take in only the first ten values from this iterate method

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and then it's going to print the values and it is going to stop the stream.

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So this is all about the iterate method.

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The next step is we'll go ahead and explore the generate method.

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So if we type in the stream class, it has the generate method and as you see, it is taking a supplier

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as an input.

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What I'm going to do, I'm going to create a supplier instance and this is going to be of type integer.

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I'm going to just name it as integer supplier.

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In here, what we are going to do, we are going to make use of the random class, which is part of

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the Java API itself.

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And we are going to.

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Let's import this first.

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So what are the methods it supports?

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There is this method called next end, which is going to give you some random values.

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Let's make use of that.

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So generate.

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And in here I'm going to pass the supplier.

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A player.

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Sorry.

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Integers, a player.

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That's it.

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What it is going to do.

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It is going to generate again infinite streams.

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I would like to print this first and then show you what's happening there.

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And then we'll use a limit function to limit the values, to limit the values from the generate method.

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I'm going to run this.

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There you go.

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It printed all these random integers which was generated by this next int method.

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So I want to limit this for just five values so that we can see what's happening there.

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There you go.

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It just printed the Pi values.

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All these values came from the next INT method, which is randomly generating an integer using the random

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class.

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So this is all about the of iterate and generate method.

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You can use this method whenever you need an on demand stream based on your use case, you can provide

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the values or you can implement your own functionalities.

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Here.

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With this, we came to the end of this tutorial.

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Thank you for watching.