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Now one common source of confusion.

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I want to clarify here is the difference between generics and union types.

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Why could you confuse these two.

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Well for example our data storage here.

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If we're accepting generic types based on these types we could all rewrite that to just say well we

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want to store strings or numbers or billions in here.

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Right.

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So we could store that or to be precise.

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Wrap this in parentheses so that we say either of these types as an array.

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And then here of course we could also say well what we get here when we add item is either a string

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a number or boolean we remove it.

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It's the same.

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Now what's the problem with this approach.

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On first sight it might look like it achieves the same but actually does something totally different.

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What we're saying here is we're storing any kind of data in there as long as it's ever in the array

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of strings numbers are billions.

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And we're also then adding any kind of data here even a string a number or boolean and the same for

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removing and we already got some errors down there of course because it can't initialized isn't a generic

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way anymore.

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But other than that it works.

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Now the problem however is for one up here we're not saying this is ever an array of strings or in arrays

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of numbers or an array of ebullience.

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This says well we got an array which can have strings numbers and boolean is mixed.

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So if we would want to say either an array of strings or an array of numbers we would have to say string

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array number array or boolean array.

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Well we can do that but now we get a problem here.

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Now we're adding a string a number or a boolean but depending on what we actually set this data array

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to be either a number array or a billionaire rate where a string array we're not allowed to add a number

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or a boolean or a string.

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If we set this to be a String array well then we can't add a number here yet here I am fine with any

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parameter as long as it is a number boolean or string.

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So the problem is here with union types we accept any of these values every time this method gets called

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or this method.

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So we're not saying hey whenever we're working with this class you have to decide for one type and then

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stick to it.

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Instead we're saying whenever you're calling this method you're free to use any of these types.

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And that's exactly not what we want here.

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If a reverts this to the previous setup where we used generic types

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then we got a different setup here we say you got to choose ones which kind of data you want to store

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and then you're only allowed to add that exact type of data so yea if I add a number for example I get

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an error because that's not a string and I chose that I only want to manage strings here.

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When I set the generic type and that's the difference between union types and generic types union types

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can be great.

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If you want to have a function which you can call with one of these types every time you call it generic

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types are great.

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If you want to lock in a certain type you is the same type throughout the entire class instance you

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create you use the same type throughout the entire function that's where you want the generic type you

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want union types when you are flexible to have a different type with every method call with every function

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call then you can use union types generic types lock in a type.