learning/katas/java/Core Transforms/Combine/Combine PerKey/src/Task.java

/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
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 *  See the License for the specific language governing permissions and
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import org.apache.beam.sdk.Pipeline;
import org.apache.beam.sdk.options.PipelineOptions;
import org.apache.beam.sdk.options.PipelineOptionsFactory;
import org.apache.beam.sdk.transforms.Combine;
import org.apache.beam.sdk.transforms.Combine.BinaryCombineFn;
import org.apache.beam.sdk.transforms.Create;
import org.apache.beam.sdk.values.KV;
import org.apache.beam.sdk.values.PCollection;
import util.Log;

class Task {

  static final String PLAYER_1 = "Player 1";
  static final String PLAYER_2 = "Player 2";
  static final String PLAYER_3 = "Player 3";

  public static void main(String[] args) {
    PipelineOptions options = PipelineOptionsFactory.fromArgs(args).create();
    Pipeline pipeline = Pipeline.create(options);

    PCollection<KV<String, Integer>> scores =
        pipeline.apply(
            Create.of(
                KV.of(PLAYER_1, 15), KV.of(PLAYER_2, 10), KV.of(PLAYER_1, 100),
                KV.of(PLAYER_3, 25), KV.of(PLAYER_2, 75)
            ));

    PCollection<KV<String, Integer>> output = applyTransform(scores);

    output.apply(Log.ofElements());

    pipeline.run();
  }

  static PCollection<KV<String, Integer>> applyTransform(PCollection<KV<String, Integer>> input) {
    return input.apply(Combine.perKey(new SumIntBinaryCombineFn()));
  }

  static class SumIntBinaryCombineFn extends BinaryCombineFn<Integer> {

    @Override
    public Integer apply(Integer left, Integer right) {
      return left + right;
    }

  }

}