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使用 Hadoop mapreduce 我正在编写代码来获取不同长度的子字符串。给定字符串“ZYXCBA”和长度为 3 的示例。我的代码必须返回所有可能的长度为 3 的字符串（“ZYX”、“YXC”、“XCB”、“CBA”），长度为 4（“ZYXC”、“YXCB”、 "XCBA") 最后长度为 5("ZYXCB","YXCBA")。

在地图阶段，我做了以下事情：

key = 我想要的子字符串的长度

值 = "ZYXCBA"。

所以映射器输出是

3,"ZYXCBA"
4,"ZYXCBA"
5,"ZYXCBA"

在reduce中，我使用字符串（“ZYXCBA”）和键3来获取长度为3的所有子字符串。4,5也是如此。结果收集在一个 ArrayList 中。

我正在使用以下命令运行我的代码：

hduser@Ganesh:~/Documents$ hadoop jar Saishingles.jar hadoopshingles.Saishingles Behara/Shingles/input Behara/Shingles/output

我的代码如下所示::

package hadoopshingles;

import java.io.IOException;

import java.util.ArrayList;

import org.apache.hadoop.fs.Path; 

import org.apache.hadoop.io.IntWritable;

import org.apache.hadoop.io.Text;

import org.apache.hadoop.mapreduce.Mapper;

import org.apache.hadoop.mapreduce.Reducer;

import org.apache.hadoop.conf.Configuration;

import org.apache.hadoop.mapreduce.Job;

import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;

import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;


public class Saishingles{

public static class shinglesmapper extends Mapper<Object, Text, IntWritable, Text>{

        public void map(Object key, Text value, Context context
                ) throws IOException, InterruptedException {

            String str = new String(value.toString());
            String[] list = str.split(" ");
            int index = Integer.parseInt(list[0]);
            String val = list[1];
            int length = val.length();
            for(int i = index; i <= length; i++)
            {
                context.write(new IntWritable(index),new Text(val));
            }       
        }

     }


public static class shinglesreducer extends Reducer<IntWritable,Text,IntWritable,ArrayList<String>> {
    private ArrayList<String> result = new ArrayList<String>();

    public void reduce(IntWritable key, Text value, Context context
            ) throws IOException, InterruptedException {
        String str = new String(value.toString());
        int newkey = key.get();
        int Tz = str.length() - newkey + 1;
        int position = 0;
        while (position <= Tz)
        {
            result.add(str.substring(position,position + newkey -1));
            position = position + 1;
        }   
        context.write(new IntWritable(newkey),result);
    }
}





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

      Configuration conf = new Configuration();
      Job job = Job.getInstance(conf, "Saishingles");
      job.setJarByClass(hadoopshingles.Saishingles.class);
      job.setMapperClass(shinglesmapper.class);
      job.setCombinerClass(shinglesreducer.class);
      job.setReducerClass(shinglesreducer.class);
      job.setMapOutputKeyClass(IntWritable.class);
      job.setMapOutputValueClass(Text.class);
      job.setOutputKeyClass(IntWritable.class);
      job.setOutputValueClass(ArrayList.class);
      FileInputFormat.addInputPath(job, new Path(args[0]));
      FileOutputFormat.setOutputPath(job, new Path(args[1]));
      System.exit(job.waitForCompletion(true) ? 0 : 1);

}

}

它给出了以下错误：

Exception in thread "main" java.lang.ClassNotFoundException: hadoopshingles.Saishingles
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:278)
    at org.apache.hadoop.util.RunJar.run(RunJar.java:214)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:136)

请帮助我，提前谢谢你:)

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1 回答 1

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我相信你不应该在类名中包含“ .class ”。

代替

job.setJarByClass(hadoopshingles.Saishingles.class);

它应该是

job.setJarByClass(hadoopshingles.Saishingles);

于 2016-07-20T13:47:30.320 回答