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https://issues.apache.org/jira/browse/LUCENE-2308?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13094514#comment-13094514
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Uwe Schindler commented on LUCENE-2308:
---------------------------------------
I am on opposite side:
In general the constructor of the immutable class is hidden (package-private or
private depending on class hierarchy). So nobody can use it. The only API the
user sees is the builder pattern. By that we only have *one* API and one usage
type.
Builder patterns can be formatted very nice and it does not matter if people do:
{code:java}
Field.Builder b = new Field.Builder();
b.setFoo();
b.setBar();
Field f = b.build();
{code}
versus
{code:java}
Field f = new Field.Builder()
.setFoo()
.setBar()
.build();
{code}
The last chaining one is even more readable, and that is why *I* prefer
builders. A so called "telescoping constructor" is the antipattern because its
completely unreadable, as Java lacks of named parameters [the best example is
WordDelimiterFilter, that one is horrible - a typical candidate for
WordDelimiterFilter.Builder subclass). The chaining code is for stack based
machines like the JVM and the x86 processors also more natural than the first
one. The return value of the previous call resides already on the stack after
the method returns, but instead of popping it and pushing again, it can stay
there and you simply add the parameters of the next method call. This leads to
also very elegant bytecode, for which hotspot has optimizations :-)
About code duplication: You can in the hidden ctor of the immutable class make
a clone of the builder and keep it somewhere private final inside the instance.
This one then holds the unmodifiable instance state.
About number of objects (yes, we have the builder object and possibly a clone
to it as suggested before and finally the immutable object): The number of
objects is really nonsense here as all of those will be created in the Eden
space and disappear as soon as the loop/method exits. You can try autoboxing
with a recent JavaVM - you would in most cases see no slowdown caused by
autoboxing. These are problems from pre-2000 when we had Java 1.1.
Uwe
> Separately specify a field's type
> ---------------------------------
>
> Key: LUCENE-2308
> URL: https://issues.apache.org/jira/browse/LUCENE-2308
> Project: Lucene - Java
> Issue Type: Improvement
> Components: core/index
> Reporter: Michael McCandless
> Assignee: Michael McCandless
> Labels: gsoc2011, lucene-gsoc-11, mentor
> Fix For: 4.0
>
> Attachments: LUCENE-2308-10.patch, LUCENE-2308-11.patch,
> LUCENE-2308-12.patch, LUCENE-2308-13.patch, LUCENE-2308-14.patch,
> LUCENE-2308-15.patch, LUCENE-2308-16.patch, LUCENE-2308-17.patch,
> LUCENE-2308-18.patch, LUCENE-2308-19.patch, LUCENE-2308-2.patch,
> LUCENE-2308-20.patch, LUCENE-2308-21.patch, LUCENE-2308-3.patch,
> LUCENE-2308-4.patch, LUCENE-2308-5.patch, LUCENE-2308-6.patch,
> LUCENE-2308-7.patch, LUCENE-2308-8.patch, LUCENE-2308-9.patch,
> LUCENE-2308-branch.patch, LUCENE-2308-final.patch, LUCENE-2308-ltc.patch,
> LUCENE-2308-merge-1.patch, LUCENE-2308-merge-2.patch,
> LUCENE-2308-merge-3.patch, LUCENE-2308.branchdiffs,
> LUCENE-2308.branchdiffs.moved, LUCENE-2308.patch, LUCENE-2308.patch,
> LUCENE-2308.patch, LUCENE-2308.patch, LUCENE-2308.patch
>
>
> This came up from dicussions on IRC. I'm summarizing here...
> Today when you make a Field to add to a document you can set things
> index or not, stored or not, analyzed or not, details like omitTfAP,
> omitNorms, index term vectors (separately controlling
> offsets/positions), etc.
> I think we should factor these out into a new class (FieldType?).
> Then you could re-use this FieldType instance across multiple fields.
> The Field instance would still hold the actual value.
> We could then do per-field analyzers by adding a setAnalyzer on the
> FieldType, instead of the separate PerFieldAnalzyerWrapper (likewise
> for per-field codecs (with flex), where we now have
> PerFieldCodecWrapper).
> This would NOT be a schema! It's just refactoring what we already
> specify today. EG it's not serialized into the index.
> This has been discussed before, and I know Michael Busch opened a more
> ambitious (I think?) issue. I think this is a good first baby step. We could
> consider a hierarchy of FIeldType (NumericFieldType, etc.) but maybe hold
> off on that for starters...
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