wangxianghu commented on a change in pull request #2222:
URL: https://github.com/apache/hudi/pull/2222#discussion_r517821503



##########
File path: 
hudi-client/hudi-java-client/src/main/java/org/apache/hudi/client/common/HoodieJavaEngineContext.java
##########
@@ -0,0 +1,84 @@
+/*
+ * 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,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hudi.client.common;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hudi.client.common.function.SerializableConsumer;
+import org.apache.hudi.client.common.function.SerializableFunction;
+import org.apache.hudi.client.common.function.SerializablePairFunction;
+import org.apache.hudi.common.config.SerializableConfiguration;
+import org.apache.hudi.common.util.Option;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Stream;
+
+import static java.util.stream.Collectors.toList;
+import static 
org.apache.hudi.client.common.function.FunctionWrapper.throwingFlatMapWrapper;
+import static 
org.apache.hudi.client.common.function.FunctionWrapper.throwingForeachWrapper;
+import static 
org.apache.hudi.client.common.function.FunctionWrapper.throwingMapToPairWrapper;
+import static 
org.apache.hudi.client.common.function.FunctionWrapper.throwingMapWrapper;
+
+/**
+ * A java engine implementation of HoodieEngineContext.
+ */
+public class HoodieJavaEngineContext extends HoodieEngineContext {
+
+  public HoodieJavaEngineContext(Configuration conf, TaskContextSupplier 
taskContextSupplier) {
+    super(new SerializableConfiguration(conf), taskContextSupplier);
+  }
+
+  @Override
+  public <I, O> List<O> map(List<I> data, SerializableFunction<I, O> func, int 
parallelism) {
+    return 
data.stream().parallel().map(throwingMapWrapper(func)).collect(toList());
+  }
+
+  @Override
+  public <I, O> List<O> flatMap(List<I> data, SerializableFunction<I, 
Stream<O>> func, int parallelism) {
+    return 
data.stream().parallel().flatMap(throwingFlatMapWrapper(func)).collect(toList());
+  }
+
+  @Override
+  public <I> void foreach(List<I> data, SerializableConsumer<I> consumer, int 
parallelism) {
+    data.stream().forEach(throwingForeachWrapper(consumer));
+  }
+
+  @Override
+  public <I, K, V> Map<K, V> mapToPair(List<I> data, 
SerializablePairFunction<I, K, V> func, Integer parallelism) {
+    Map<K, V> map = new HashMap<>();
+    data.stream().map(throwingMapToPairWrapper(func)).forEach(x -> 
map.put(x._1, x._2));
+    return map;

Review comment:
       > Can I ask what are the benefits of the new implementation?
   
   logically,the latter is the same as SparkRDD‘s `MapToPair`, identical keys 
are not allowed
   and it is more elegant in code style I think.
   It is just advice, no big deal :)




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