hadoop 分布式文件系统 wordcount 示例答案

【问题标题】：hadoop distributed file system wordcount examplehadoop 分布式文件系统 wordcount 示例
【发布时间】：2014-05-14 19:30:46
【问题描述】：

public class WordCount {

   public static class Map extends MapReduceBase implements Mapper<LongWritable, Text, Text, IntWritable> {
     private final static IntWritable one = new IntWritable(1);
     private Text word = new Text();

     public void map(LongWritable key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
       String line = value.toString();
       StringTokenizer tokenizer = new StringTokenizer(line);
       while (tokenizer.hasMoreTokens()) {
         word.set(tokenizer.nextToken());
         output.collect(word, one);
       }
     }
   }

   public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable> {
     public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException {
       int sum = 0;
       while (values.hasNext()) {
         sum += values.next().get();
       }
       output.collect(key, new IntWritable(sum));
     }
   }

   public static void main(String[] args) throws Exception {

     JobConf conf = new JobConf(WordCount.class);
     conf.setJobName("wordcount");

     conf.setOutputKeyClass(Text.class);
     conf.setOutputValueClass(IntWritable.class);

     conf.setMapperClass(Map.class);
     conf.setCombinerClass(Reduce.class);
     conf.setReducerClass(Reduce.class);

     conf.setInputFormat(TextInputFormat.class);
     conf.setOutputFormat(TextOutputFormat.class);

     FileInputFormat.setInputPaths(conf, new Path(args[0]));
     FileOutputFormat.setOutputPath(conf, new Path(args[1]));

     JobClient.runJob(conf);
     }
}

错误：

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at org.myorg.WordCount.main(WordCount.java:64)

我是hadoop的菜鸟，请帮助我

【问题讨论】：

请先拿一本关于 Java 的书，这根本不是 Hadoop 的问题。
你用什么命令来运行这个程序...？

标签： java eclipse hadoop

【解决方案1】：

这意味着你没有使用任何命令行参数运行你的程序，如果你检查 args.length 你会看到它是零，所以运行带有输入/和输出/规范的命令..

【讨论】：