1 hadoop根目录下新建存放自己编写的wordcount的文件夹：
1.1 mkdir playground
1.2 mkdir playground/src
1.3 mkdir playground/classes
2 将编写的wordcount放到src目录下：
3 编译
javac -classpath hadoop-core-1.0.3.jar:hadoop-tools-1.0.3.jar:lib/commons-cli-1.2.jar -d playground/classes playground/src/WordCount.java
4 打包
jar -cvf playground/wordcount.jar -C playground/classes/ .
5 运行
bin/hadoop jar playground/wordcount.jar org.apache.hadoop.examples.WordCount input output
over:
察看结果：
bin/hadoop dfs -cat output/*
