Example 1: Finding aggregate of stream elements usingStream.reduce()method Example 1-Java 8 code showing Stream.reduce() method for aggregation //Employee.java package com.javabrahman.java8; public class Employee{ private String name; private Integer age; private Double salary; public Employee(Stri...
In the example, we create a list of users. The example calculates the age of the oldest user. int maxAge = users.stream().mapToInt(User::getAge).reduce(0, Math::max); From the list we create a Java stream. The stream is mapped to anIntStreamwith amapToIntmethod. Finally, there...
0row(s)in0.0850seconds hbase(main):004:0>put'test','row2','cf:b','value2' 0row(s)in0.0110seconds hbase(main):005:0>put'test','row3','cf:c','value3' 0row(s)in0.0100seconds 我们在创建的表中加入了三个值,第一次在“row1”行“cf:a”列插入了一个值“value1”,以此...
A parallel stream may make the accumulation work in a fashion like:7 + 3 + 5 + 1 == (7 + 3) + (5 + 1) But, these demands effectively bar you from using some types of operations with the reduce() method. You cannot, for example, do subtraction operations with reduce(). That ...
reduce 是数组迭代器(https://jrsinclair.com/articles/2017/javascript-without-loops/)里的瑞士军刀。它强大到您可以使用它去构建大多数其他数组迭代器方法,例如 .map()、 .filter() 及 .flatMap()。在这篇文章中,我们将带你用它来做...
importjava.util.ArrayList;importjava.util.List;importjava.util.Optional;publicclassReduceExample{publicstaticvoidmain(String[]args){List<Integer>numbers=newArrayList<>();numbers.add(1);numbers.add(2);numbers.add(3);numbers.add(4);numbers.add(5);Optional<Integer>sum=numbers.stream().reduce((a,...
yarn jar /usr/hdp/current/hadoop-mapreduce-client/hadoop-mapreduce-examples.jar wordcount /example/data/gutenberg/davinci.txt /example/data/davinciwordcount 将从/example/data/gutenberg/davinci.txt读取此作业的输入。 此示例的输出存储于/example/data/davinciwordcount中。 两个路径皆位于群集的默认存储,...
此示例位于群集默认存储的 /example/jars/hadoop-mapreduce-examples.jar 中。 以下Java 代码是包含在 hadoop-mapreduce-examples.jar 文件中的 MapReduce 应用程序的源代码: Java 复制 package org.apache.hadoop.examples; import java.io.IOException; import java.util.StringTokenizer; import org.apache.hadoop...
mvn archetype:generate -DgroupId=org.apache.hadoop.examples -DartifactId=wordcountjava -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false This command creates a directory with the name specified by theartifactIDparameter (wordcountjavain this example.) This directory contains the...
首先,使用JAVA IDEA软件新建项目CountByData,并利用该软件编译并自动生成jar包: 然后在项目中添加如下代码段: <dependencies> <dependency> <groupId>org.apache.hadoop</groupId> <artifactId>hadoop-common</artifactId> <version>3.1.4</version> </dependency> ...