我正在学习 Apache Hadoop,并且正在查看 WordCount 示例org.apache.hadoop.examples.WordCount。我已经理解这个例子,但是我可以看到变量LongWritable 键没有用于
(...)
public void map(LongWritable key, Text value,
OutputCollector<Text, IntWritable> output,
Reporter reporter) throws IOException {
String line = value.toString();
StringTokenizer itr = new StringTokenizer(line);
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
output.collect(word, one);
}
}
(...)
这个变量有什么用?有人可以给我一个简单的例子吗?谢谢