第一天：Java源码级实战速成（通过动手实战类、对象等，通过Spark和Hadoop案例代码和源码解析具体指知识的应用、深度详解匿名接口在Spark开发中的运用）

 

call回调

  /**
   *  Return a new RDD by first applying a function to all elements of this
   *  RDD, and then flattening the results.
   */
  def flatMap[U](f: FlatMapFunction[T, U]): JavaRDD[U] = {
    import scala.collection.JavaConverters._
    def fn: (T) => Iterable[U] = (x: T) => f.call(x).asScala
    JavaRDD.fromRDD(rdd.flatMap(fn)(fakeClassTag[U]))(fakeClassTag[U])
  }

 

 

 

/*
 * 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 com.dt.spark.java.cores;

import scala.Tuple2;
import scala.annotation.serializable;

import org.apache.spark.SparkConf;
import org.apache.spark.api.java.JavaPairRDD;
import org.apache.spark.api.java.JavaRDD;
import org.apache.spark.api.java.JavaSparkContext;
import org.apache.spark.api.java.function.FlatMapFunction;
import org.apache.spark.api.java.function.Function2;
import org.apache.spark.api.java.function.PairFunction;

import java.util.Arrays;
import java.util.List;
import java.util.regex.Pattern;

public final class JavaWordCount  extends serializable{
  private static final Pattern SPACE = Pattern.compile(" ");

  public static void main(String[] args) throws Exception {

  /*  if (args.length < 1) {
      System.err.println("Usage: JavaWordCount ");
      System.exit(1);
    }*/

    SparkConf sparkConf = new SparkConf().setAppName("JavaWordCount").setMaster("local");
    JavaSparkContext ctx = new JavaSparkContext(sparkConf);
   
    //JavaRDD lines = ctx.textFile(args[0], 1);
    JavaRDD lines = ctx.textFile( "G://IMFBigDataSpark2016//Bigdata_Software//spark-1.6.0-bin-hadoop2.6//spark-1.6.0-bin-hadoop2.6//spark-1.6.0-bin-hadoop2.6//README.md");
 
    JavaRDD words = lines.flatMap(new FlatMapFunction() {
      /**
   *
   */
  private static final long serialVersionUID = 1L;

 @Override
      public Iterable call(String s) {
        return Arrays.asList(SPACE.split(s));
      }
    });

    JavaPairRDD ones = words.mapToPair(new PairFunction() {
      @Override
      public Tuple2 call(String s) {
        return new Tuple2(s, 1);
      }
    });

    JavaPairRDD counts = ones.reduceByKey(new Function2() {
      @Override
      public Integer call(Integer i1, Integer i2) {
        return i1 + i2;
      }
    });

    List output = counts.collect();
    for (Tuple2 tuple : output) {
      System.out.println(tuple._1() + ": " + tuple._2());
    }
    ctx.stop();
  }
}