在Hadoop中,无法直接使用getFileName()方法获取文件名并显示其格式,这是因为Hadoop是一个分布式文件系统,它将文件切分成多个块并存储在不同的节点上。在Hadoop中,文件名和文件格式信息是存储在文件系统的元数据中的,而不是直接与文件本身关联。
要获取文件名和显示其格式,可以通过使用Hadoop的API来实现。以下是一种可能的方法:
示例代码:
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.Path;
public class HadoopFileExample {
public static void main(String[] args) {
try {
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
Path filePath = new Path("hdfs://<namenode>:<port>/path/to/file");
FileStatus fileStatus = fs.getFileStatus(filePath);
String fileName = filePath.getName();
String fileFormat = fileStatus.getLen();
System.out.println("File Name: " + fileName);
System.out.println("File Format: " + fileFormat);
} catch (Exception e) {
e.printStackTrace();
}
}
}
请注意,上述示例代码中的<namenode>
和<port>
应替换为实际的Hadoop集群的名称节点和端口。
示例代码:
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class WordCount {
public static class TokenizerMapper extends Mapper<Object, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
String[] words = value.toString().split("\\s+");
for (String word : words) {
this.word.set(word);
context.write(this.word, one);
}
}
}
public static class IntSumReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
private IntWritable result = new IntWritable();
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
for (IntWritable val : values) {
sum += val.get();
}
result.set(sum);
context.write(key, result);
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
Job job = Job.getInstance(conf, "word count");
job.setJarByClass(WordCount.class);
job.setMapperClass(TokenizerMapper.class);
job.setCombinerClass(IntSumReducer.class);
job.setReducerClass(IntSumReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
上述示例代码是一个简单的Word计数示例,它将输入文件中的单词进行计数,并输出每个单词及其出现次数。
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