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Question about Effective Java

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I'm trying to understand the example on page 14 of Effective Java by Joshua 
Bloch (Second Edition). I hope someone here can help.

Here's the code from the book for the sake of those who don't have the book 
(or the same edition of the book):
=======================================================================
//Builder Pattern
public class NutritionFacts {
	private final int servingSize;
	private final int servings;
	private final int calories;
	private final int fat;
	private final int sodium;
	private final int carbohydrate;
	
	public static class Builder {
		//Required parameters
		private final int servingSize;
		private final int servings;
		
		//Option parameters - initialized to default values
		private int calories = 0;
		private int fat = 0;
		private int carbohydrate = 0;
		private int sodium = 0;
		
		public Builder(int servingSize, int servings) {
			this.servingSize = servingSize;
			this.servings = servings;
		}
		
		public Builder calories(int val) {
			this.calories = val;
			return this;
		}
		
		public Builder fat(int val) {
			this.fat = val;
			return this;
		}
		
		public Builder carbohydrate(int val) {
			this.carbohydrate = val;
			return this;
		}
		
		public Builder sodium(int val) {
			this.sodium = val;
			return this;
		}
		
		public NutritionFacts build() {
			return new NutritionFacts(this);
		}
	}
	private NutritionFacts(Builder builder) {
		this.servingSize = builder.servingSize;
		this.servings = builder.servings;
		this.calories = builder.calories;
		this.fat = builder.fat;
		this.sodium = builder.sodium;
		this.carbohydrate = builder.carbohydrate;
		
	}

}=======================================================================

I should start by saying I have successfully imitated the example in my own 
code. I'm just not entirely sure what it is doing. 

Bloch clearly intends this technique as a way to avoid the confusion of 
methods where you simply have a long list of parameters and could easily 
enter parameters out of order. The code on page 15 shows how much clearer 
things are when you use his technique; all of the optional parameters can 
have clear names so that you know what each one is. I really like this; I 
think it's MUCH better than simply listing a bunch of different integers 
and hoping you assign each one to the right variable. In a nutshell, I get 
what he is doing but I'm just not sure how this code works. 

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? They aren't constructors and they only 
deal with one data value, fat or calories or whatever, but they apparently 
return a complete Builder.

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 
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?
- I get "access to enclosing constructor NutritionFacts
(NutritionFacts.Builder) is emulated by a synthetic accessor method" in the 
return statement of the build() method (Eclipse offers to remove the 
"private" from the constructor for NutritionFacts OR to add 
"@SuppressWarnings - synthetic access" to NutritionFacts but I'm not sure 
which is better and why. 
- I get "read access to enclosing field NutritionFacts.Builder.servingSize 
is emulated by a synthetic accessor method" (Eclipse offers to remove the 
"private" from the variables in Builder OR to add "@SuppressWarnings - 
synthetic access" to NutritionFacts but I'm not sure which is better and 
why. 

-- 
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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