Hadoop单机环境配置OK后，需要找个例子测试一下Mapreduce功能。因此从Hadoop源代码中找到一个例子:WordCount.java，来验证。
编译过程如下：
cd hadoop-example/ javac -classpath ../hadoop-2.1.0-beta/share/hadoop/common/hadoop-common-2.1.0-beta.jar:../hadoop-2.1.0-beta/share/hadoop/common/lib/commons-cli-1.2.jar:../hadoop-2.1.0-beta/share/hadoop/mapreduce/hadoop-mapreduce-client-core-2.1.0-beta.jar:../hadoop-2.1.0-beta/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-2.1.0-beta.jar -d WordCount WordCount.java cd WordCount jar -cfe WordCount.jar org.apache.hadoop.examples.WordCount org/* hadoop fs -put helloworld.txt hadoop jar WordCount.jar /user/root/helloworld.txt ./result
hadoop-example和hadoop-2.1.0-beta在同一级目录。
helloworld.txt的内容为：
Hello
World
nihao
wohao
Hello
Hello
World
计算结果：
Hello 3
World 2
nihao 1
wohao 1
Hadoop版本：Hadoop 2.1.0-beta
配置过程可参考博客中前几篇文章
