package ${package};
import eu.stratosphere.api.java.DataSet;
import eu.stratosphere.api.java.ExecutionEnvironment;
import eu.stratosphere.api.java.aggregation.Aggregations;
import eu.stratosphere.api.java.functions.FlatMapFunction;
import eu.stratosphere.api.java.tuple.Tuple2;
import eu.stratosphere.util.Collector;
/**
* Implements the "WordCount" program that computes a simple word occurrence histogram
* over some sample data
*
* <p>
* This example shows how to:
* <ul>
* <li>write a simple Stratosphere program.
* <li>use Tuple data types.
* <li>write and use user-defined functions.
* </ul>
*
*/
@SuppressWarnings("serial")
public class WordCountJob {
//
// Program.
//
public static void main(String[] args) throws Exception {
// set up the execution environment
final ExecutionEnvironment env = ExecutionEnvironment.getExecutionEnvironment();
// get input data
DataSet<String> text = env.fromElements(
"To be, or not to be,--that is the question:--",
"Whether 'tis nobler in the mind to suffer",
"The slings and arrows of outrageous fortune",
"Or to take arms against a sea of troubles,"
);
DataSet<Tuple2<String, Integer>> counts =
// split up the lines in pairs (2-tuples) containing: (word,1)
text.flatMap(new LineSplitter())
// group by the tuple field "0" and sum up tuple field "1"
.groupBy(0)
.aggregate(Aggregations.SUM, 1);
// emit result
counts.print();
// execute program
env.execute("WordCount Example");
}
//
// User Functions
//
/**
* Implements the string tokenizer that splits sentences into words as a user-defined
* FlatMapFunction. The function takes a line (String) and splits it into
* multiple pairs in the form of "(word,1)" (Tuple2<String, Integer>).
*/
public static final class LineSplitter extends FlatMapFunction<String, Tuple2<String, Integer>> {
@Override
public void flatMap(String value, Collector<Tuple2<String, Integer>> out) {
// normalize and split the line
String[] tokens = value.toLowerCase().split("\\W+");
// emit the pairs
for (String token : tokens) {
if (token.length() > 0) {
out.collect(new Tuple2<String, Integer>(token, 1));
}
}
}
}
}