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All right, we've set up our classes now we need to inject some logic into them.

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Going back to requirements, talked text, and from first glance, it seems that we need to force every

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child the class to override two common methods.

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Deposit and withdraw.

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And to do that, we need to define two abstract methods inside the parent class.

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So we'll go to account Java.

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And here we'll see.

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Public.

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Abstract void, and it will deposit some amount of money, double amounts.

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Now, a withdrawal can be successful or it can fail.

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So here we'll say public.

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Abstract bullying.

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That can withdraw some amount of money.

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All right, and as we override, deposit and withdraw, we need to define this protected method inside

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of account Java.

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Remember, that protected means this method is only accessible from within its children.

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It's not public, which means you can't access it from anywhere.

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It's protected only child.

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The classes, checking savings and loan can access the ruined method.

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Anyways, we seem to be getting an error.

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OK, got an important decimal format before we can use it, and we're good.

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And now remember that if a parent defines an abstract method, the child class is forced to override

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it.

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So we'll go to checking.

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That's why we're seeing these errors.

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Checking needs to provide its own logic for deposit and withdraw.

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OK, so I'll just override them for now.

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We won't provide any logic just yet.

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Not until we write unit tests.

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Checking we'll do the same thing for savings.

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And.

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Merge doing that to get rid of the areas for now.

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Now, the reason I'm not writing the logic just yet is because we need to unit test all of the behavior

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inside of the requirements that text filed before we write the code for it.

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That way, we make sure that any code we write, any logic we provide doesn't have any bugs.

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So long as every test passes, we know that we're good.

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So I'll go to a count tests that Java and I'll start by on commenting the accounts array.

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And that doesn't seem to be like a good amount of indentation, so I'll fix that and import the accounts

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class.

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And now, before running each test, we got to make sure the array is being populated first, so we'll

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start by annotating a method with before this before method is going to run before each test.

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Public void setup.

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Where we set up our accounts are by going back over to learn the parts and populating it with three

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objects.

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Checking.

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Savings.

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That did not work.

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And loan.

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OK, perfect.

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We're going to start by unit testing the behavior for withdrawing.

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We want to make sure the correct amount gets withdrawn from the checking account under normal circumstances.

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So what we'll do is create a unit test.

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Public void would draw.

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And what we need to do is withdraw from the checking account that's at index zero.

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So accounts.

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At Index zero, that would draw.

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And we're going to withdraw 14 40.

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Then we'll make an assertion assert equals.

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The assertion expects eighty four point five one after we get the account balance accounts out of like

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zero dark get balance.

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So instead of checking, not Java.

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We'll update the current balance, SuperDart set balance.

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By minus thing, the amount from the current balance.

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All right, and before we run our tests, let's just return true by default.

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We'll address that later on.

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Now we can run our test and see if it works.

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And it still fails, and it seems like the value is off by decimal points, because this is money,

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we're going to round to two decimal points.

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So what we can do is call the protected method super dot around.

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Right over here.

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Rerun your test.

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And perfect.

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OK, now looking back at the requirements, now we're going to unit test this behavior.

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The checking account charges an overdraft fee of five dollars and fifty cents if the amount being withdrawn

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exceeds the account balance.

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So we want to make sure this overdraft fee gets deducted if they try to withdraw more than what's in

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their balance.

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So back here?

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We'll create another unit tests.

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Test.

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And the unit test will be called overdraft public void overdraft.

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And we need to withdraw from the checking account and index zero.

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So we'll say accounts and index zero, that would draw.

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And we'll be withdrawing fifteen thirty four point forty three.

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And then here we'll make an assertion will assert equals.

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The expected value is negative $15 and 42 cents after we get the account's balance accounts at index

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zero, don't get balance.

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Run the test, and it obviously should fail.

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Now we can write code to make it pass.

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So back in checking.

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We'll see if.

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The current balance to get balance minus the amount being withdrawn.

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Smaller than zero.

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Then we'll update the current balance, super accept balance, super tight get balance.

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Minus amounts.

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Minus five dollars and fifty cents.

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But hold on a second.

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This seems like a pretty important value.

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So it'd be safer to use a constant tear instead.

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So what I'll do is I'll declare a private.

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Static final double overdraft fee.

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Is equal to five dollars and fifty cents.

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And will use that constant instead.

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Because there's no risk of accidentally changing a constant.

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All right, and in the event that this if statement gets executed, we want to break the entire function

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by returning crew here because obviously you don't want this to run.

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And then that's true and that will just mess everything up.

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So we'll go back to account tests, run the test.

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And once again, with doubles, we got the issue of having way too many decimal points, we're dealing

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with money, so we went around to two decimal places.

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So over here.

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And checking, we'll have to call SuperDart around.

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We were on the test.

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OK.

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Back door requirements, that text will a unit test this behavior?

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We want to make sure that withdrawal doesn't happen if the amount surpasses the overdraft limit.

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So we'll create a unit test.

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Public.

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Void.

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Overdraft limit.

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Inside, I'm going to withdraw.

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Seventeen twenty six from the checking accounts.

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And then we're going to assert that the resulting balance shouldn't change, it should remain.

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Uh, fifteen twenty four point five one.

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When we get the account balance accounts, zero, don't get balance.

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OK.

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Run the test.

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And it fails.

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Now we just got to write code to make it pass.

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Back here, we'll check if the current balance.

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If super don't get balance minus amounts.

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Is smaller than negative 200, then well, wait a second.

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This seems like an important value, and it would be safer once again to use a constant here instead.

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So we'll declare a private static.

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Final double.

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Constant named overdraft limit equal to $200.

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And we'll say if superdog, that balance minus amount is smaller than the overdraft limit.

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Then we'll just return false.

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That will break the entire function.

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Let's make this an if.

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And you know what?

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Let's just create a chain of if else.

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That looks a lot better to me.

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All right.

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We can rerun our test.

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And that works perfect.

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All right, back here, the next piece of behavior we're going to unit test is the withdrawal fee.

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We want to make sure that it's charged a $5 fee if they attempt to withdraw from a savings account.

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So we'll create a unit test.

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Test.

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Public void, withdrawal fee.

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And we're going to withdraw $100 from the savings accounts, accounts and index one.

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Well, withdraw $100.

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And then we're going to make an assertion that the resulting balance is twenty one hundred thirty six

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dollars point sixty cents as we get the current balance for the savings account.

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Count that index one, don't get balance.

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All right.

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Run the test.

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And it fails.

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Now we just got to write code to make it past so inside the redraw method for savings.

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We'll update the balance super set balance.

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We'll get the current balance, super Typekit balance.

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Minus the amount.

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Minus $5.

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Once again, $5, it seems like an important value, so we're going to declare it as a constant here,

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we'll say private static.

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Final double.

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What drove the.

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Is equal to $5.

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And here we'll use a constant instead.

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And, as always, will around to two decimal places.

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And return true to indicate that the withdrawal was successful.

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Now, usually in a savings account, you shouldn't be able to make a withdrawal that exceeds your balance.

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But it didn't say anything in the requirements tax.

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So whatever in the Java world, we're going to permit it.

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Run the test.

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And it passes.

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All right, we're going to continue with the remaining tasks in the next video.