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

1. Title:
   Calculate Price Method
2. Description:

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   Earlier, we saw that we could pass
   a number into the display method.
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   Let's talk more about the different
   inputs and output of a method.
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   Let's look at the submitOrder method
   in the MainActivity as an example.
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   Say you have a bunch of lines
   of code in that method.
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   When the user clicks
   on the Order button,
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   it will trigger this submitOrder
   method to be called.
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   The Android device will execute each of
   these instructions from top to bottom,
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    and when it hits the calculatePrice
    method call it will
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    jump over to where the calculatePrice
    method is defined.
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    Say that this is defined at
    the bottom of the MainActivity file.
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    The Android device will execute each of
    these instructions from top to bottom of
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    the method, and then it will jump
    back to the submitOrder method.
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    Then, it will continue executing these
    instructions until it hits the end
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    of the method.
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    When the calculatePrice
    method is called,
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    we can pass a bunch of inputs over so
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    that when we're executing these lines
    of code, we can use these input values.
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    As a result of this method,
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    we can pass a single output
    value back to the caller.
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    That way, the output value can be
    used in the subsequent lines of code.
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    In Java, we call the inputs to
    a method input parameters, and
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    we can have zero or
    more input parameters.
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    In Java,
    we call the output a return value,
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    and we can have zero or
    one return value.
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    An example of an input parameter
    is passing the quantity
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    over to the calculatePrice method.
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    That way, this method can use the
    quantity to figure out the total price
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    of the whole order.
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    Then, we can pass that total
    price back as a return value.
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    And then in the submitOrder method,
    down here,
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    we can use this total price to do other
    things, like display it onscreen, or
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    create receipt, or anything like that.
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    So to summarize, this is where we
    define the calculatePrice method, and
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    this is where we call it.
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    We want to create a method to
    calculate the price of a coffee order.
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    Currently, we calculate the price
    directly in the submitOrder method, but
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    the logic to calculate the price is
    going to get a little more complicated.
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    So let's move it into its own method.
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    Then we can call it as many times
    as we want without copying and
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    pasting the code everywhere.
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    As you gain more experience in Android
    development, you'll gain better judgment
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    on when to create a new method for
    something or when you don't need to.
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    This will just come with more
    experience and more time.
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    So, this is the first time
    we're going to be creating
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    a new method in
    the MainActivity on our own.
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    Instead of starting by writing it from
    scratch, we want to start by learning to
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    recognize what is a correct method
    by reading some code snippets.
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    So in the instructor notes, we're
    going to provide you three options.
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    Read over these three code snippets and
    determine which
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    option correctly implements the method
    to calculate the price of the order.
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    When you click on the link
    in the instructor notes,
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    you'll see this just has code for
    options A, B, and C.
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    The goal here is for
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    you to become comfortable with reading
    code that you've never seen before.
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    We haven't gone over the exact rules for
    what makes a valid method, but
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    I want you to make your best guess on
    which option you think is most correct.
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    I also encourage you
    to Google search for
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    more information on how
    to define Java methods.
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    As you click through
    the different search results,
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    you'll come across information in the
    documentation that you don't understand.
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    But I want you to become comfortable
    with not understanding everything on
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    those pages, because it's perfectly
    normal to not understand everything.
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    All you need to do is just skim
    the articles for what you understand and
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    what you think is relevant
    to the problem at hand.
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    So, go ahead and read the code for
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    these three options, look up some
    information online, and then make your
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    best guest on how to correctly
    define the calculatePrice method.