MapReduce之WordCount

这是我在学习《深入理解Hadoop》中的代码示例，仅作示例用

package edu.hfut.wls.study.hadoop;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.conf.Configured;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.LongWritable;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.input.TextInputFormat;import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;import org.apache.hadoop.util.GenericOptionsParser;import org.apache.hadoop.util.Tool;import org.apache.hadoop.util.ToolRunner;import java.io.IOException;/** * Created by lianbin.zlb. */public class WordCount extends Configured implements Tool{    @Override    public int run(String[] strings) {        try {            Job job = Job.getInstance(getConf());            job.setJarByClass(WordCount.class);            job.setOutputKeyClass(Text.class);            job.setOutputValueClass(LongWritable.class);            job.setMapperClass(WcMapper.class);            job.setReducerClass(WcReducer.class);            job.setInputFormatClass(TextInputFormat.class);            job.setOutputFormatClass(TextOutputFormat.class);            String[] args = new GenericOptionsParser(getConf(), strings).getRemainingArgs();            FileInputFormat.setInputPaths(job, new Path(args[0]));            FileOutputFormat.setOutputPath(job, new Path(args[1]));            job.submit();        } catch (Exception e) {            e.printStackTrace();        }        return 0;    }    public static class WcMapper extends Mapper<LongWritable, Text, Text, LongWritable>{        @Override        protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {            String mVal = value.toString();            context.write(new Text(mVal), new LongWritable(1));        }    }    public static class WcReducer extends Reducer<Text, LongWritable, Text, LongWritable>{        @Override        protected void reduce(Text key, Iterable<LongWritable> values, Context context) throws IOException, InterruptedException {            long sum = 0;            for(LongWritable lVal : values){                sum += lVal.get();            }            context.write(key, new LongWritable(sum));        }    }    public static void main(String[] args) throws Exception {        Configuration conf = new Configuration();        ToolRunner.run(new WordCount(), args);    }}