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well hello internet and welcome to part 21 of my design patterns video tutorial today we're going to talk about an extremely simple design pattern and that is known as the proxy design pattern so what is the proxy design pattern well the proxy is a class which is going to be used to limit access to another class and you may do this for security reasons because an object is intensive to create or that object is in a remote location that you'd like to have a proxy or a thing that sort of decides what methods are available what fields are available from that outside object but in this part of the tutorial I'm basically a focus on the security aspect of the proxy design pattern because there's numerous ways to use it which I'm going to get into at a later date so here is the basic class diagram for the proxy design pattern you have from the last part of the tutorial which was the state design pattern which is available in the lower left-hand corner if you want to completely understand what's going on here I created a basic interface for an ATM machine now this ATM machine of course allows you to access and receive cash now of course I'm sure you could understand why that could be a security concern if in an outside program we wanted to be able to access this ATM machine class object so what we're going to do is we're going to throw a proxy object in between and only allow the client in this situation that is protected because both the proxy as well as the protected object are going to implement the same interface what the proxy is going to do is limit access to fields an ATM machine to just getting the ATMs current state and the amount of cash in the machine we're not going to allow them to set the amount of cash the machine or take money out of the machine and that is going to be this part of the tutorial so let's get into the code okay so here I am in get ATM data and this is going to act as an interface that both the ATM machine as well as our proxy are going to implement so I'm going to define inside of this interface those methods that I want those using this proxy to be able to access in regards to our ATM machine and I'm just going to come in here and to find them so I think it's perfectly safe to be able to get the current state of the ATM machine or what the ATM machine is currently doing because no damage can be done in regards to just getting that information and I also think it would be perfectly fine to tell them how much cash is in the machine so we're basically implementing this as if this would be at a bank office in which a manager would want to access and make sure ATM machines are running properly so there we go get ATM data Java is done so the next thing we're going to do is go into the ATM machine dot Java which we created in the last part of the tutorial and to use this guy we're going to come in here and just type in implements get ATM data now this is going to be able to properly work with our proxy just put our mouse over top of this guy right here ATM machine and add-on implemented methods that are forced because we implemented get ATM data and you can see that both of them popped up down here so down here and get ATM data we're just getting rid of this and then down here for return just to keep this very simple I'm gonna say ATM state and that's going to get the gist of how the ATM machine is going to be running going to pass back object information but either way that's definitely enough and then down here in get cash in machine we're going to return cash in machine which is up here so I might as well just copy that like I said this would be set up so that a branch manager for example would be able to figure out if a machine ran out of cash that's all we need to do ATM machine is now set up so that we'll be able to get that information next thing we need to do is set up ATM proxy Java jump in here in this situation the proxy is going to both create and destroy ATM machine objects and provide access only to those methods that we would consider to be safe so get ATM data going to implement the same interface very simple and then what's it going to do it's going to say hey you need to implement some methods here and there it goes and unimplemented methods and there they are now this is an act a go-between between our regular ATM machines so what we're going to want to do here is actually create ATM machines inside of this proxy so very very simple if they would call get ATM state we're going to say ATM machine and then I can call it real ATM machine is equal to new ATM machine and create an ATM machine object and then in the return area I'm going to go real ATM machine paste that inside of there put a dot and one of these methods is going to be get ATM data which we can see right here just click on that and then throw a semicolon in there so that's going to create a new machine however just allow access to this very specific method which is also the same exact name as what we have right there and then down here we're going to do pretty much exactly the same thing with get cashing machine so create a new object and then down here in the return statement you're going to go return and then we're going to say click and one of these is going to be get cash in machine boom there that goes and there that goes and this is done now you have your proxy finished now it's time to go into test ATM machine and see if everything worked so we're just going to come in here the bottom of what we created in the last part of the tutorial and start working with this guy so I'm going to go ATM get ATM data which is the interface they get ATM data and we're going to call this real ATM machine is equal to new ATM machine and this is also going to lock it out from only being able to access those methods that are defined inside of it and then we're also going to create the proxy which is going to stand in between it and I'm going to call this ATM proxy is equal to new ATM proxy I'll save and then I'm going to print out some information from there print line throw a new line in there just for the heck of it and go current ATM state and then if I want to access it I can go ATM proxy boom and then you're going to see here what pops up none of the secret information that we wouldn't want to show up however it will pop up get ATM data so I'm going to click on that and then I'm also going come and do something very similar here we're going to print out the amount of cash in the machine to cash in ATM machine and all this codes available in a link underneath the video and then once again if we go into the proxy that we just created here we're going to see get cashing machine is one of the things available however set cash and machine and all the potentially dangerous methods are not close that off and you will not be able to do things like say ATM proxy set cash in machine because that is not defined in the interface and just in case you are wondering I think you can see the red mark underneath our C doesn't work and even though I did create rule ATM I'm also not going to be able to use that to access that method you may ask yourself well why not same reason we have over here it is part of the interface get ATM data so and get ATM data is the version that I am using right here so that blocks out potentially harmful methods however if we save this and execute it you're going to see that it's going to give me the information that I do need which is the current state which means there's no card currently in the ATM machine and the total amount of cash in the ATM machine which is $2,000 so there's a basic overview of the proxy design pattern like I said before it could be used in numerous different ways and we'll get into that later parts of the tutorial if you have any questions of course take a look at the code underneath the video and if you don't see your questions answered there leave a any questions or comments below otherwise till next time