11TopN实战
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1、Java版本：
1.1、取前3
package sparkcore.java;
import java.util.List;
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.Function;
import org.apache.spark.api.java.function.PairFunction;
import scala.Tuple2;
/**
* 取前3
*/
public class Top3 {
public static void main(String[] args) {
SparkConf conf = new SparkConf()
.setAppName("Top3")
.setMaster("local");
JavaSparkContext sc = new JavaSparkContext(conf);
/*
3
5
6
7
1
4
5
6
9
0
3
*/
JavaRDD<String> lines = sc.textFile("top.txt");
JavaPairRDD<Integer, String> pairs = lines.mapToPair(
new PairFunction<String, Integer, String>() {
private static final long serialVersionUID = 1L;
@Override
public Tuple2<Integer, String> call(String t) throws Exception {
return new Tuple2<Integer, String>(Integer.valueOf(t), t);
}
});
JavaPairRDD<Integer, String> sortedPairs = pairs.sortByKey(false);
JavaRDD<Integer> sortedNumbers = sortedPairs.map(
new Function<Tuple2<Integer,String>, Integer>() {
private static final long serialVersionUID = 1L;
@Override
public Integer call(Tuple2<Integer, String> v1) throws Exception {
return v1._1;
}
});
List<Integer> sortedNumberList = sortedNumbers.take(3);
for(Integer num : sortedNumberList) {
System.out.println(num);
}
sc.close();
}
}
输出：
9
7
61.2、每组内取top3
package sparkcore.java;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
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.PairFunction;
import org.apache.spark.api.java.function.VoidFunction;
import scala.Tuple2;
/**
* 每组内取top3
*/
public class GroupTop3 {
public static void main(String[] args) {
SparkConf conf = new SparkConf().setAppName("Top3").setMaster("local");
JavaSparkContext sc = new JavaSparkContext(conf);
/*
class1 90
class2 56
class1 87
class1 76
class2 88
class1 95
class1 74
class2 87
class2 67
class2 77
*/
JavaRDD<String> lines = sc.textFile("score.txt");
JavaPairRDD<String, Integer> pairs = lines.mapToPair(
new PairFunction<String, String, Integer>() {
private static final long serialVersionUID = 1L;
@Override
public Tuple2<String, Integer> call(String line) throws Exception {
String[] lineSplited = line.split(" ");
return new Tuple2<String, Integer>(lineSplited[0], Integer.valueOf(lineSplited[1]));
}
});
JavaPairRDD<String, Iterable<Integer>> groupedPairs = pairs.groupByKey();
JavaPairRDD<String, Iterable<Integer>> top3Score = groupedPairs.mapToPair(
new PairFunction<Tuple2<String, Iterable<Integer>>, String, Iterable<Integer>>() {
private static final long serialVersionUID = 1L;
@Override
public Tuple2<String, Iterable<Integer>> call(Tuple2<String, Iterable<Integer>> classScores)
throws Exception {
Integer[] top3 = new Integer[3];
String className = classScores._1;
Iterator<Integer> scores = classScores._2.iterator();
List<Integer> l = new ArrayList<Integer>();
while (scores.hasNext()) {
l.add(scores.next());
}
Collections.sort(l, new Comparator<Integer>() {
public int compare(Integer o1, Integer o2) {
return -o1.compareTo(o2);
}
});
for (int i = 0; i < l.size(); i++) {
if (i < 3) {
top3[i] = l.get(i);
}
}
return new Tuple2<String, Iterable<Integer>>(className, Arrays.asList(top3));
}
});
top3Score.foreach(new VoidFunction<Tuple2<String, Iterable<Integer>>>() {
private static final long serialVersionUID = 1L;
@Override
public void call(Tuple2<String, Iterable<Integer>> t) throws Exception {
System.out.println("class: " + t._1);
Iterator<Integer> scoreIterator = t._2.iterator();
while (scoreIterator.hasNext()) {
Integer score = scoreIterator.next();
System.out.println(score);
}
System.out.println("=======================================");
}
});
sc.close();
}
}
输出：
class: class1
95
90
87
=======================================
class: class2
88
87
77
=======================================2、Scala版本：
2.1、取前3
package sparkcore.scala
import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
object Top3 {
def main(args: Array[String]): Unit = {
val conf = new SparkConf()
.setAppName("Top3")
.setMaster("local")
val sc = new SparkContext(conf)
val lines = sc.textFile("top.txt", 1)
val pairs = lines.map { line => (line.toInt, line) }
val sortedPairs = pairs.sortByKey(false)
val sortedNumbers = sortedPairs.map(sortedPair => sortedPair._1)
val top3Number = sortedNumbers.take(3)
for (num <- top3Number) {
println(num)
}
}
}输出：
9
7
62.2、每组内取top3
package sparkcore.scala
import org.apache.spark.SparkConf
import org.apache.spark.SparkContext
object GroupTop3 {
def main(args: Array[String]): Unit = {
val conf = new SparkConf()
.setAppName("Top3")
.setMaster("local")
val sc = new SparkContext(conf)
val lines = sc.textFile("score.txt", 1)
val linePair = lines.map((line => (line.split(" ")(0), line.split(" ")(1).toInt)))
val groupRdd = linePair.groupByKey()
val sortRdd = groupRdd.map(g => (g._1,
g._2.toList.sorted(new Ordering[Int]() {
def compare(x: Int, y: Int): Int = {
- x.compare(y)
}
}).take(3)))
sortRdd.foreach(e => println(e._1 + " : " + e._2))
}
}
输出：
class1 : List(95, 90, 87)
class2 : List(88, 87, 77)以上是关于11TopN实战的主要内容，如果未能解决你的问题，请参考以下文章