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

1. Title:
   Add or Remove Parameters
2. Description:

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   I'm going to walk you through
   an example of a method with a different
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   number of input parameters.
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   I started by creating a new app from
   the project wizard in Android Studio, so
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   this is completely unrelated
   to the Just Java app.
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   I added this method
   in the main activity.
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   It's called createWeatherMessage.
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   There's no input parameters, and
   the return value is a string.
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    This method is supposed to create a new
    message that specifies the city name and
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    the temperature.
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    You can think of a method as
    being a template of instructions.
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    So I can make temperature
    be an input parameter.
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    And it's a number, so
    I'm going to say, int temperature.
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    And then I can use this right here.
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    So, this is a string literal, and
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    then it's concatenated with
    the temperature integer.
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    And then it's concatenated with another
    string that says degrees Fahrenheit.
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    So now the message can be customized
    based on the temperature because it's
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    an input parameter.
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    Oh yeah, I forgot to mention this
    earlier, but in the onCreate method of
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    the main activity, which is called
    when the activity gets created,
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    I can call the createWeatherMessage.
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    Before I passed in no arguments, but
    now we have one required parameter.
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    So I'm going to pass in 77 for
    the temperature.
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    Now that makes the error go away,
    and this method call is correct.
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    The other thing I should modify
    is this comment on the method.
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    I'm going to add a blank line, and
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    then I'll start to describe the input
    parameter which is temperature here.
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    I'm going to type @param temperature,
    and
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    then I can add a description saying that
    this is the temperature of the city.
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    Sometimes the parameter names
    are a little hard to understand, so
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    that's why the description is useful.
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    Other times if your method is public
    then other people will be able
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    to call this method, and
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    they might not know what
    are the instructions inside this method.
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    So reading this java doc and
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    the description of the parameters
    is really useful to them.
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    I mentioned earlier that
    a method is like a template.
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    So, what if we want to change the city
    so that it's not always San Francisco?
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    I can make city be an input parameter.
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    So I can just add a comma here.
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    And since city name is text I'm
    going to make it a string data type.
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    Then I can delete San Francisco and
    replace it with a variable city name.
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    And remember to add a space before and
    after here as well.
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    Cool, so
    now this method can create a message
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    that's customizable to
    a certain city and temperature.
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    I also remembered to
    modify the java doc so
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    that it has this extra parameter and
    description for a city name.
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    Since I changed the method signature,
    now I have an error up here.
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    The method no longer works
    with just one argument.
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    I need to pass in two arguments.
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    So I add a comma and
    then pass in San Francisco string.
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    Now the error goes away.
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    So when I call createWeatherMessage(77,
    it's going to be value of temperature,
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    and San Francisco will be
    the value of city name.
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    And it will create
    the proper string here.
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    Now we're going to go back to
    the calculate price method,
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    and we're going to modify
    the method signature so
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    that it has a different
    number of input parameters.
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    We're going to define it with zero
    input parameters, one input parameter,
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    and lastly,
    try it with two input parameters.
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    You'll see how changing the method
    signature here to have a different
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    number of input parameters with affect
    the way that the method is called.
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    Normally when you're building your app,
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    you will just define it one way with
    a certain number of input parameters.
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    And usually that number of input
    parameters is going to be determined
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    based off of what's
    happening inside the method.
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    The best practice is to
    only pass input parameters
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    that you're actually going
    to need inside this method.
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    There's no point in passing over more
    information if you're not going to
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    use it inside here.
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    Here are the instructions for this task.
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    First define the calculate price method
    in your app in the main activity.
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    See the instrructor notes for
    a code snippet that you can start with.
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    We're going to modify
    the calculatePrice method so
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    that it only has one input parameter.
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    Then in the submitOrder method
    call calculatePrice and
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    pass in quantity as the input.
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    Then try to modify the calculatePrice
    method to have two input parameters.
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    That way in the submitOrder method you
    will call calculatePrice quantity and
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    then you can pass in the price
    which could be $10 for example.
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    And lastly, try changing calculatePrice
    so that it has zero input parameters.
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    That way in the submitOrder method
    you would just call calculatePrice
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    like this.
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    Let's do the first one together so
    you understand what I mean.
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    I'm going to open up the link
    in the instructor notes.
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    In this gist we provided code for
    the calculatePrice method.
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    So go ahead and
    select everything and then copy it.
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    In Android Studio,
    I'm going to paste in this method.
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    I'm just going to paste it in
    right below submitOrder, and
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    I'll make sure that there's a blank
    line in between each method here.
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    That makes it easier to read.
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    Then I can call this method
    from the submitOrder method.
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    I'm just going to insert the call
    at the very bottom of the method.
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    Later we're going to integrate
    it with the code up here.
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    But for now, this is good.
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    Oops, I forgot that we have one input
    parameter, so I need a pass quantity.
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    Now do the same for
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     the remaining two tasks by modifying
     the input parameters here.
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     To complete this task,
     if you need examples to reference,
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     you can always do a Google search for
     Java methods.