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
     
       {	//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
     
       {	public void reduce(Text key, Iterable
      
        iterable, Context context)			throws IOException, InterruptedException {		// process values		int 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.xml		Job 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);	}}