package algorithm;import java.io.IOException;
import java.util.StringTokenizer;import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;//前两个参数是固定的后两个根据需要修改  第四个参数我改成了IntWritable  比int写的快
public class TestMapper1 extends Mapper<LongWritable, Text, Text, IntWritable> {//key是行好  value是哪一行内容//文件多少行 map调用多少次public void map(LongWritable key, Text value, Context context)throws IOException, InterruptedException {String line = value.toString();StringTokenizer st = new StringTokenizer(line);while(st.hasMoreElements()) {String word = st.nextToken();context.write(new Text(word), new IntWritable(1));//map的输出}}}

package algorithm;import java.io.IOException;import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;public class TestReduce1 extends Reducer<Text, IntWritable, Text, IntWritable> {public void reduce(Text key, Iterable<IntWritable> iterable, Context context)throws IOException, InterruptedException {// process valuesint sum = 0;for (IntWritable val : iterable) {sum += val.get();//get转为整数}context.write(key, new IntWritable(sum));}}

package algorithm;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;public class Mapreduce1 {public static void main(String[] args) throws Exception {Configuration conf = new Configuration(); //对应于mapred-site.xmlJob job = new Job(conf,"WordCount");job.setJarByClass(Mapreduce1.class);job.setMapperClass(TestMapper1.class);job.setReducerClass(TestReduce1.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(IntWritable.class);job.setNumReduceTasks(1);//"/in"解析不了  提示文件不存在 因为把他们认为是本地文件了 因为有个 file:/FileInputFormat.addInputPath(job, new Path("hdfs://192.168.58.180:8020/in"));//输出文件不能存在   FileOutputFormat.setOutputPath(job, new Path("hdfs://192.168.58.180:8020/wordcount"));System.exit(job.waitForCompletion(true) ? 0 : 1);}
}