Question

我的Java版本：

➜  test git:(dev) ✗ java -version
java version "1.8.0_131"
Java(TM) SE Runtime Environment (build 1.8.0_131-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.131-b11, mixed mode)

我正在尝试运行以下简单的java程序，该程序使用来自here的hadoop map reduce从文件中提供单词计数。以下是整个java代码：

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapred.*;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

public class WordCount extends Configured implements Tool {
   private final static LongWritable ONE = new LongWritable(1L);

// Mapper Class, Counts words in each line. For each line, break the line into words and emits them as (word, 1)

public static class MapClass 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 itr = new StringTokenizer(line);
  while (itr.hasMoreTokens()) {
    word.set(itr.nextToken());
     output.collect(word, one);
   }
 }
}

// Reducer class that just emits the sum of the input values.

public static class Reduce extends MapReduceBase implements Reducer< Text, IntWritable, Text, IntWritable > {
public void reduce(Text key, Iterator 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));
    }
  }

static int printUsage() {
System.out.println("wordcount [-m #mappers ] [-r #reducers] input_file output_file");
    ToolRunner.printGenericCommandUsage(System.out);
    return -1;
  }

public int run(String[] args) throws Exception {

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

// the keys are words (strings)
   conf.setOutputKeyClass(Text.class);
// the values are counts (ints)
   conf.setOutputValueClass(IntWritable.class);

   conf.setMapperClass(MapClass.class);
// Here we set the combiner!!!!
   conf.setCombinerClass(Reduce.class);
   conf.setReducerClass(Reduce.class);

  List other_args = new ArrayList();
   for(int i=0; i < args.length; ++i) {
     try {
        if ("-m".equals(args[i])) {
conf.setNumMapTasks(Integer.parseInt(args[++i]));
        } else if ("-r".equals(args[i])) {
conf.setNumReduceTasks(Integer.parseInt(args[++i]));
        } else {
          other_args.add(args[i]);
        }
      } catch (NumberFormatException except) {
        System.out.println("ERROR: Integer expected instead of " + args[i]);
        return printUsage();
      } catch (ArrayIndexOutOfBoundsException except) {
        System.out.println("ERROR: Required parameter missing from " +
            args[i-1]);
        return printUsage();
      }
    }
// Make sure there are exactly 2 parameters left.
   if (other_args.size() != 2) {
      System.out.println("ERROR: Wrong number of parameters: " +
          other_args.size() + " instead of 2.");
      return printUsage();
    }
    FileInputFormat.setInputPaths(conf, other_args.get(0));
    FileOutputFormat.setOutputPath(conf, new Path(other_args.get(1)));

    JobClient.runJob(conf);
    return 0;
  }

public static void main(String[] args) throws Exception {
    int res = ToolRunner.run(new Configuration(), new WordCount(), args);
    System.exit(res);
  }
}

但是在上面代码的下面部分：

// Reducer class that just emits the sum of the input values.

public static class Reduce extends MapReduceBase implements Reducer< Text, IntWritable, Text, IntWritable > {
public void reduce(Text key, Iterator 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));
    }
  }

我遇到编译错误：

➜测试git :( dev）✗javacWordCount.java   WordCount.java:43：错误：＆gt;预期    OutputCollector输出，                                     ^

WordCount.java:43：错误：＆＃39;）＆＃39;预期    OutputCollector输出，                                      ^

WordCount.java:43：错误：＆＃39;;＆＃39;预期    OutputCollector输出，                                        ^

WordCount.java:43：错误：预期    OutputCollector输出，                                                ^

WordCount.java:44：错误：＆＃39;;＆＃39;预期    记者报道）抛出IOException {            ^

WordCount.java:44：错误：预期    记者报道）抛出IOException {                     ^   WordCount.java:44：错误：非法启动类型    记者报道）抛出IOException {                       ^

WordCount.java:44：错误：＆＃39;;＆＃39;预期    记者报道）抛出IOException {                                         ^

8个错误

我确信这是一个非常基本的错误，但无法弄清楚。

Answer 1

我不确定这是什么，但它不是Java。例如：

OutputCollector<text, intwritable="">

text和intwrtiable不是类型。那应该是Text和IntWritable。默认分配给我一个完整的秘密。 Java并不支持默认的泛型，即使它确实如此，我也不确定空字符串在这种情况下的含义。

在java程序中编译错误以使用hadoop计算文件中的单词

1 个答案: