Showing Revision 3 created 05/25/2016 by Udacity Robot.

1. Title:
   Use Return Value from Method - Solution
2. Description:

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   First we're going to modify
   the calculatePrice method signature
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   to have the correct return data type.
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   We're also going to assume that
   there's 0 input parameters.
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   This is where the calculatePrice
   method is defined.
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   The purpose of this method is to
   calculate the total price of the order
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   and then return that.
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   The price should be an integer so
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    we should change the return
    data type from void to int.
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    That takes care of the first task.
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    The quiz also said to make sure that
    there's no input parameters, and
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    that's what we have here.
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    Now the second task is to
    modify the inside of the method
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    to make sure that we're computing
    the correct price for the order.
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    And assuming $5.00 for a cup of coffee.
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    Inside this method we're taking
    the quantity of cups ordered.
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    And we're multiplying it
    by $5 per cup of coffee.
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    This equals the total order price.
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    So this line of code is cracked.
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    But there's two issues that I see,
    the variable price is never used and
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    there's an error that says
    missing return statement.
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    It's expecting us to return an integer,
    but we're not returning anything.
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    Right now our code is the same
    as if we just said this.
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    We need a line that says return and
    then actually put a value here and
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    the value on return is a price.
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    So, I'm just going to put price,
    which is a variable we defined up here.
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    Cool, so now all the errors go away.
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    We should also modify the Java DOC.
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    So that we specify that we're
    turning the total price.
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    That way when someone's calling this
    method, they know what to expect.
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    Okay, so now we finished all
    the parts for defining this method.
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    Now, let's move on to where
    the method is getting called.
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    Within the submitOrder method, we
    should call the calculatePrice method.
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    Currently calculate price,
    is floating in the middle of nowhere.
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    I'm going to copy it, and
    I'm going to paste it up here.
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    Because before we would calculate
    the price of the order in line,
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    in the submit order method, but
    now we have a method for it.
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    So I'm going to paste this here.
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    Now get rid of the extra semicolon.
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    You'll notice that price is a local
    variable in this method, and
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    also in this method.
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    It's okay if they have the same name,
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    because these are different
    variable scopes.
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    So the price variable here is totally
    unrelated with the variable here.
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    They're updated and
    created independently from each other.
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    And once this method finishes executing,
    this price variable is gone.
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    Okay back to our submitOrder method.
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    So we calculated a price and
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    stored it in a variable, and then we
    can use it to create the price message.
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    So, actually,
    all of this code can stay the same.
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    We're concatenating the integer,
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    price, to the string total
    with the currency symbol.
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    Then we concatenate "Thank you!" and
    then just display it on the screen.
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    So I'm going to erase these extra,
    blank lines, and save it, and
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    then we can run it on our device.
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    Okay, so I changed the quantity, and
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    hit ORDER, then it correctly
    shows $25 as the price.
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    Awesome, it worked.
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    But how can I be sure that
    calculatePrice is actually
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    working because there's no user visible
    change compared to our app from before.
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    Here are a couple of techniques that
    you can do to verify that your code is
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    actually running.
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    I could have it return a really
    crazy number, like 700.
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    Save my code and then run it.
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    Now what I expect to see is
    if I change the quantity and
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    hit the ORDER button,
    it should saw that the price is $700.
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    That way I'll know that this calculate
    price method is actually getting called.
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    And it does, cool.
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    Now I can revert this change.
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    Another way to check that this
    method is getting executed
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    is to add a break point here.
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    So I'm going to click on
    this little bug icon and
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    then our apple enter debug mode.
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    If I change the quantity and
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    I hit order, then I expect that
    the app will pause at this point.
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    And it does.
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    So now we're in
    the calculate price method.
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    There is a global variable, quantity.
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    And if I step over to the next line then
    I see that there's now a local variable,
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    price And it's set to be $15 because
    quantity is 3, 3 times 5 is 15, cool.
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    So, it's going through
    the calculated price method, and
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    if I hit Resume,
    then it updates properly on this screen.