如文件word.txt内容如下：

what is you name?

my name is zhang san。

要求统计word.txt中出现“is”的次数？

 

代码如下：

PerWordMapper

package com.hadoop.wordcount;import java.io.IOException;import java.util.StringTokenizer;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Mapper;public class PerWordMapper extends Mapper
    
      {	public Text keyText = new Text();	public IntWritable intValue = new IntWritable(1);		@Override	protected void map(Object key, Text value,			Context context)			throws IOException, InterruptedException {		String str = value.toString();		StringTokenizer to = new StringTokenizer(str);		while (to.hasMoreTokens()) {			String t = to.nextToken();			//此处为判断统计字符串的地方			if(t.equals("is")){				keyText = new Text(t);				context.write(keyText, intValue);			}	       	     }	}}
    

 

PerWordReducer

package com.hadoop.wordcount;import java.io.IOException;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.Text;import org.apache.hadoop.mapreduce.Reducer;public class PerWordReducer extends Reducer
    
      {	public IntWritable intValue = new IntWritable(0);	@Override	protected void reduce(Text key, Iterable
     
       value,			Context context)			throws IOException, InterruptedException {		int sum = 0;		while(value.iterator().hasNext()){			sum += value.iterator().next().get();		}		intValue.set(sum);		context.write(key, intValue);	}	}
     
    

PerWordCount

package com.hadoop.wordcount;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.lib.input.FileInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.util.GenericOptionsParser;import com.hadoop.mapreducer.MapperClass;import com.hadoop.mapreducer.ReducerClass;import com.hadoop.mapreducer.WordCount;public class PerWordCount {	public static void main(String[] args) throws IOException, InterruptedException, ClassNotFoundException {		Configuration conf = new Configuration();	    String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();	    System.out.println("otherArgs.length:"+otherArgs.length);	    if (otherArgs.length != 2) {	      System.err.println("Usage: wordcount 
     
     
      ");	      System.exit(2);	    }	    Job job = new Job(conf, "word count");	    job.setJarByClass(PerWordCount.class);	    job.setMapperClass(PerWordMapper.class);	    job.setCombinerClass(PerWordReducer.class);	    job.setReducerClass(PerWordReducer.class);	    job.setOutputKeyClass(Text.class);	    job.setOutputValueClass(IntWritable.class);	    FileInputFormat.addInputPath(job, new Path(otherArgs[0]));	    FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));	    System.exit(job.waitForCompletion(true) ? 0 : 1);	}}