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

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<Object, Text, Text, IntWritable> {            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

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<Text, IntWritable, Text, IntWritable> {            public IntWritable intValue = new IntWritable(0);        @Override        protected void reduce(Text key, Iterable<IntWritable> 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);        }            }  

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 <in> <out>");              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);        }        }