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https://issues.apache.org/jira/browse/MAHOUT-162?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12746770#action_12746770
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Sean Owen commented on MAHOUT-162:
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Doesn't a lot more than this fail in Java 6, like @Override on implemented
interface methods? or are you compiling with 6 and running on 5? If so, is this
really the only incompatible difference at runtime? Hmm, maybe so.
I do echo Ted's comment that switching to Java 6 is a good idea but understand
that is sometimes easier said than done. Since the project is officially on
Java 6, I'd hesitate to have an informal requirement to not use any new APIs in
6. I do agree, this was a good API change that avoids an unnecessary and
annoying exception. Still, one could say, it's such a small change to create
backwards compatibility.
I'm going to suggest you simply reuse and change the code for Java 5 for now,
and if you move to Java 6 later, you can quite easily use the standard
implementation.
> Added support for mapping String to long IDs in CF code
> -------------------------------------------------------
>
> Key: MAHOUT-162
> URL: https://issues.apache.org/jira/browse/MAHOUT-162
> Project: Mahout
> Issue Type: Improvement
> Components: Collaborative Filtering
> Affects Versions: 0.2
> Reporter: Sean Owen
> Assignee: Sean Owen
> Fix For: 0.2
>
> Attachments: MAHOUT-162.patch
>
>
> Since the framework now only allows long (64-bit integer) IDs, and no longer
> Strings, we need to provide some support for translating between the two. The
> basic proposal is this:
> - Define a one-way mapping from Strings to longs that is repeatable and easy
> to implement in many contexts. In particular I propose using the bottom 64
> bits of the MD5 hash of a string.
> - Define support for storing the reverse mapping (longs to Strings) in
> various ways, in an efficient way, that handles gracefully the very rare
> possibility of collision
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