Trevor Robinson created MAPREDUCE-5020:
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Summary: Compile failure with JDK8
Key: MAPREDUCE-5020
URL: https://issues.apache.org/jira/browse/MAPREDUCE-5020
Project: Hadoop Map/Reduce
Issue Type: Bug
Components: client
Affects Versions: 2.0.3-alpha
Environment: java version "1.8.0-ea"
Java(TM) SE Runtime Environment (build 1.8.0-ea-b36e)
Java HotSpot(TM) Client VM (build 25.0-b04, mixed mode)
Reporter: Trevor Robinson
Compiling `org/apache/hadoop/mapreduce/lib/partition/InputSampler.java` fails
with the Java 8 preview compiler due to its stricter enforcement of JLS
15.12.2.6 (for [Java
5|http://docs.oracle.com/javase/specs/jls/se5.0/html/expressions.html#15.12.2.6]
or [Java
7|http://docs.oracle.com/javase/specs/jls/se7/html/jls-15.html#jls-15.12.2.6]),
which demands that methods applicable via unchecked conversion have their
return type erased:
{noformat}
[ERROR]
hadoop-common/hadoop-mapreduce-project/hadoop-mapreduce-client/hadoop-mapreduce-client-core/src/main/java/org/apache/hadoop/mapreduce/lib/partition/InputSampler.java:[320,35]
error: incompatible types: Object[] cannot be converted to K[]
{noformat}
{code}
@SuppressWarnings("unchecked") // getInputFormat, getOutputKeyComparator
public static <K,V> void writePartitionFile(Job job, Sampler<K,V> sampler)
throws IOException, ClassNotFoundException, InterruptedException {
Configuration conf = job.getConfiguration();
final InputFormat inf =
ReflectionUtils.newInstance(job.getInputFormatClass(), conf);
int numPartitions = job.getNumReduceTasks();
K[] samples = sampler.getSample(inf, job); // returns Object[] according to
JLS
{code}
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