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Re: Question about Effective Java

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markspace <-@.> wrote in news:jh13se$dve$1@dont-email.me:

> On 2/9/2012 9:54 AM, Novice wrote:
>> I'm trying to understand the example on page 14 of Effective Java by
>> Joshua 
> 
>> Questions:
>> 1. I understand that a NutritionFacts could conceivably be just a
>> servingSize and a number of servings. All of the other values are
>> optional on an individual basis: any one or more of them could be
>> there but don't need to be. Any value that is omitted takes a default
>> (of zero in this example). But why are the methods calories(), fat(),
>> carbohydrate() and sodium() each returning Builder?
> 
> 
> So you can chain calls, like the example at the top of page 15.
>
I understand that chaining is what we'd like to be able to do. I'm just 
not clear on why "this", which from the method signature is apparently a 
Builder, is being returned by those methods. It _looks_ like each of them 
is returning an entire Builder even though each only contributed one 
"fact" to the Builder.  
> 
>> They aren't constructors and they only
>> deal with one data value, fat or calories or whatever, but they
>> apparently return a complete Builder.
> 
> 
> They return a Builder object (which might be the same thing as saying
> "a complete Builder").  Constructors don't have a return type
> explicitly. Learn Java syntax.
> 
> public class Builder {
>    public Builder() {}         // constructor
>    public Builder doIt() {}    // method
> }
> 
Right; I understand that already. The phrasing of my question is probably 
weird because I can't quite understand what is happening in the example.

>>
>> I'm also having trouble understanding some of the compiler warnings
>> given to me by Eclipse (3.7.1) when I actually code the class the way
>> he has it: - I get a "not used" warning for all of the private final
>> variables in 
> 
> 
> Right, it's just a dummy example.  If you add getters to
> NutritionFacts, those warnings will go away.
> 
But the body of the NutritionFacts constructor is already setting values 
for the variables. I proved that to myself by changing the name of one of 
the NutritionFacts final variables and causing a compiler error in the 
NutritionFacts constructor. Why would getters be needed if the 
constructor is already setting values for the variables? 

> 
>> NutritionClass (Eclipse offers to delete the variables OR create
>> gettsrs and setters OR "add @SuppressWarnings - unused" for each of
>> them. I'm not fond of any of these options but what is the best thing
>> to do and why? Why does Eclipse think they are unused when the
>> NutritionFacts constructor is clearly assigning values to them?
> 
> 
> It's a Java thing.  Unused means can't be read, not is not
> initialized. 

>   Things that are initialized and then never used merit a warning
>   message. 
> 
So if I only initialize it and never read it after that, I can still get 
an "unused" message? If that is right, it explains why the NutritionFacts 
constructor code doesn't prevent the message.

I could have sworn that I've made that warning go away in the past by 
simply doing an assignment statement to give the variable a value, even 
if I never touched it again later. Maybe I'm misremembering that....  


-- 
Novice

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Question about Effective Java Novice <novice@example..com> - 2012-02-09 17:54 +0000
  Re: Question about Effective Java markspace <-@.> - 2012-02-09 10:39 -0800
    Re: Question about Effective Java Novice <novice@example..com> - 2012-02-10 00:07 +0000
      Re: Question about Effective Java markspace <-@.> - 2012-02-09 16:42 -0800
  Re: Question about Effective Java Patricia Shanahan <pats@acm.org> - 2012-02-09 14:19 -0800
    Re: Question about Effective Java Novice <novice@example..com> - 2012-02-10 00:40 +0000
      Re: Question about Effective Java Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-02-09 21:08 -0500
        Re: Question about Effective Java Lew <lewbloch@gmail.com> - 2012-02-10 09:01 -0800
  Re: Question about Effective Java "John B. Matthews" <nospam@nospam.invalid> - 2012-02-10 11:59 -0500

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