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https://issues.apache.org/jira/browse/HADOOP-1231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12518932
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Tom White commented on HADOOP-1231:
-----------------------------------
>This looks good. The only thing I noticed is that in cases where you don't
>have more detailed type information, you put in the
>default <WritableComparable,Writable,WritableComparable,Writable>, which isn't
>necessary.
If I use raw types instead of parameterized types then I get compile warnings.
E.g.
{noformat}
class MyMapper implements Mapper
{noformat}
gives a warning on the call to OutputCollector#collect:
{noformat}
[javac]
/Users/tom/Documents/workspace/hadoop-trunk/src/test/org/apache/hadoop/mapred/TestMiniMRLocalFS.java:222:
warning: [unchecked] unchecked call to collect(K,V) as a member of the raw
type org.apache.hadoop.mapred.OutputCollector
[javac] out.collect((WritableComparable) value, key);
{noformat}
With type information the warning goes:
{noformat
class MyMapper implements Mapper<WritableComparable, Writable,
WritableComparable, Writable>
{noformat}
> Add generics to Mapper and Reducer interfaces
> ---------------------------------------------
>
> Key: HADOOP-1231
> URL: https://issues.apache.org/jira/browse/HADOOP-1231
> Project: Hadoop
> Issue Type: Improvement
> Components: mapred
> Reporter: Owen O'Malley
> Assignee: Tom White
> Fix For: 0.15.0
>
> Attachments: HADOOP-1231-1.patch, HADOOP-1231.patch,
> HADOOP-1231.patch, MapReduceTypes.html
>
>
> By making the input and output types of the Mapper and Reducers generic, we
> can get the information from the classes and not require the user to set them
> in the configuration.
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