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Date: Thu, 09 Feb 2012 14:19:34 -0800
From: Patricia Shanahan <pats@acm.org>
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Subject: Re: Question about Effective Java
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On 2/9/2012 9:54 AM, Novice wrote:
> I'm trying to understand the example on page 14 of Effective Java by Joshua
> Bloch (Second Edition). I hope someone here can help.
...		
> 		public Builder sodium(int val) {
> 			this.sodium = val;
> 			return this;
> 		}
...:
> 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.
>

Don't think in terms of "return a complete Builder". Java programs do
not, and cannot, pass objects around as method arguments or results.
sodium really returns a Builder reference. A reference can either be
null or be a pointer to an object of appropriate class.

Inside sodium, "this" is a pointer to the current object. Returning it
allows chaining of several method calls.

Patricia