从下面的代码我不明白两件事： DistributedCache.addcachefile(new URI ('/.dat'), job.getconfiguration()) 我不明白uri路径必须存在于hdfs中。如果我错了，请纠正我。
那是什么 p.getname().equals() 从以下代码：

public class MyDC {

public static class MyMapper extends Mapper < LongWritable, Text, Text, Text > {

    private Map < String, String > abMap = new HashMap < String, String > ();

    private Text outputKey = new Text();

    private Text outputValue = new Text();

    protected void setup(Context context) throws
    java.io.IOException, InterruptedException {

        Path[] files = DistributedCache.getLocalCacheFiles(context.getConfiguration());

        for (Path p: files) {

            if (p.getName().equals("abc.dat")) {

                BufferedReader reader = new BufferedReader(new FileReader(p.toString()));

                String line = reader.readLine();

                while (line != null) {

                    String[] tokens = line.split("\t");

                    String ab = tokens[0];

                    String state = tokens[1];

                    abMap.put(ab, state);

                    line = reader.readLine();

                }

            }

        }

        if (abMap.isEmpty()) {

            throw new IOException("Unable to load Abbrevation data.");

        }

    }

    protected void map(LongWritable key, Text value, Context context)
    throws java.io.IOException, InterruptedException {

        String row = value.toString();

        String[] tokens = row.split("\t");

        String inab = tokens[0];

        String state = abMap.get(inab);

        outputKey.set(state);

        outputValue.set(row);

        context.write(outputKey, outputValue);

    }

}

public static void main(String[] args)
throws IOException, ClassNotFoundException, InterruptedException {

    Job job = new Job();

    job.setJarByClass(MyDC.class);

    job.setJobName("DCTest");

    job.setNumReduceTasks(0);

    try {

        DistributedCache.addCacheFile(new URI("/abc.dat"), job.getConfiguration());

    } catch (Exception e) {

        System.out.println(e);

    }

    job.setMapperClass(MyMapper.class);

    job.setMapOutputKeyClass(Text.class);

    job.setMapOutputValueClass(Text.class);

    FileInputFormat.addInputPath(job, new Path(args[0]));

    FileOutputFormat.setOutputPath(job, new Path(args[1]));

    job.waitForCompletion(true);

}

}