spark3.0教程：统计10万人的平均年龄（Java）-马育民老师

# 介绍

本例子是使用 Java 代码实现统计10万人的平均年龄，代码写法与Scala略有不同，但套路一样

# 创建工程

详见：[spark3.0教程：第一个程序-WordCount实现](https://www.malaoshi.top/show_1IX1I8nV4jl2.html "spark3.0教程：第一个程序-WordCount实现")

# Java 代码

### 生成测试数据

```
package top.malaoshi.spark.age;

import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.Random;

public class DataFileGenerator {
    private final static String[] NAMES = {"李雷","韩梅梅","lucy","lili","张三","李四","王五","杜子腾","史珍香","张吉惟","林国瑞","林玟书","林雅南","江奕云","刘柏宏","阮建安","林子帆","夏志豪","吉茹定","李中冰","黄文隆","谢彦文","傅智翔","洪振霞","刘姿婷","荣姿康","吕致盈","方一强","黎芸贵","郑伊雯","雷进宝","吴美隆","吴心真","王美珠","郭芳天","李雅惠","陈文婷","曹敏侑","王依婷","陈婉璇","吴美玉","蔡依婷","郑昌梦","林家纶","黄丽昆","李育泉","黄芸欢","吴韵如","李肇芬","卢木仲","李成白","方兆玉","刘翊惠","丁汉臻","吴佳瑞","舒绿珮","周白芷","张姿妤","张虹伦","周琼玟","倪怡芳","郭贵妃","杨佩芳","黄文旺","黄盛玫","郑丽青","许智云","张孟涵","李小爱","王恩龙","朱政廷","邓诗涵","陈政倩","吴俊伯","阮馨学","翁惠珠","吴思翰","林佩玲","邓海来","陈翊依","李建智","武淑芬","金雅琪","赖怡宜","黄育霖","张仪湖"};
    public static void main(String[] args){
        File file = new File("data/DataFile.txt");  // 生成文件存放路径
        try {
            FileWriter fileWriter = new FileWriter(file);
            Random rand = new Random();
            int namesLen = NAMES.length;
            for (int i=1;i<=100000;i++){
                String name = NAMES[rand.nextInt(namesLen)];
                fileWriter.write(name +" " + (rand.nextInt(100)+1));
                fileWriter.write(System.getProperty("line.separator"));
            }
            fileWriter.flush();
            fileWriter.close();
            System.out.println("output success");

}catch(IOException e){
            e.printStackTrace();
        }
    }
}

```

在工程下生成 `data/DataFile.txt` 文件，内容如下（第二列是年龄）：

```
周琼玟 51
武淑芬 59
谢彦文 52
江奕云 54
林国瑞 34
```

### 统计

```
package top.malaoshi.spark.age;

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.FlatMapFunction;
import org.apache.spark.api.java.function.Function;
import org.apache.spark.api.java.function.Function2;

import java.util.Arrays;
import java.util.Iterator;

public class AvgAgeCalculator2 {
    public static void main(String[] args){

SparkConf sparkConf = new SparkConf().setAppName("AvgAgeCalculator").setMaster("local[*]");
        JavaSparkContext sc = new JavaSparkContext(sparkConf);
        //读取文件
        JavaRDD<String> dataFile = sc.textFile("data/DataFile.txt");

//将每行数据，根据空格拆分，取第二个元素（年龄），转换int类型
        JavaRDD<Integer> ageData = dataFile.map(new Function<String, Integer>() {
            public Integer call(String s) throws Exception {
                return Integer.parseInt(s.split(" ")[1]);
            }
        });

//        System.out.println(ageData.collect()); // 查看算子 ageData 中的数据
//        //求出人数
        long count = ageData.count();
        //        求出年龄的和
        Integer totalAge = ageData.reduce(new Function2<Integer, Integer, Integer>() {
            @Override
            public Integer call(Integer v1, Integer v2) throws Exception {
                return v1 + v2;
            }
        });
        //平均值结果为double类型
        Double avgAge = totalAge.doubleValue()/count;
        System.out.println("totalAge:" + totalAge );
        System.out.println("count:" + count );
        System.out.println("avg：" + avgAge);

}
}
```

执行结果：

```
totalAge:5056261 // 年龄和
count:100000 // 总人数
avg：50.56261 // 平均年龄
```

原文出处：http://www.malaoshi.top/show_1GW2NFGMrVlg.html