java实现spark常用算子之Repartitions

import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.VoidFunction;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Iterator;
import java.util.List;

/**
 * repartitions 算子:
 * 增加分区，使用shuffle操作
 */
public class RepartitionsOperator {

    public static void main(String[] args){
        SparkConf conf = new SparkConf().setMaster("local").setAppName("repartitions");
        JavaSparkContext sc = new JavaSparkContext(conf);
        List<String> names = Arrays.asList("w1","w2","w3","w4","w5","w6");

        JavaRDD<String> nameRdd = sc.parallelize(names,2);

        JavaRDD<String> namefristRdd = nameRdd.mapPartitionsWithIndex(new Function2<Integer, Iterator<String>, Iterator<String>>() {
            @Override
            public Iterator<String> call(Integer index, Iterator<String> iterator) throws Exception {

                List<String> list = new ArrayList<>();
                while (iterator.hasNext()){
                    list.add("1["+index+"]"+iterator.next());
                }
                return list.iterator();
            }
        },true);

        //增加分区
        JavaRDD<String> temp = namefristRdd.repartition(5);

        JavaRDD<String> nameseconedRdd = temp.mapPartitionsWithIndex(new Function2<Integer, Iterator<String>, Iterator<String>>() {
            @Override
            public Iterator<String> call(Integer index, Iterator<String> iterator) throws Exception {
                List<String> list = new ArrayList<>();
                while (iterator.hasNext()){
                    list.add("2["+index+"]:"+iterator.next());
                }
                return list.iterator();
            }
        },false);

        nameseconedRdd.foreach(new VoidFunction<String>() {
            @Override
            public void call(String s) throws Exception {
                System.err.println(s);
            }
        });

    }
}

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