我用java编写了hadoop的程序，我想在java程序中定义自己的数据类型。这是参考资料
这是我的密码：

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;
import java.util.StringTokenizer;
import java.util.HashMap;
import java.util.Iterator;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
import java.io.DataInput; 
import java.io.DataOutput; 
import java.io.IOException; 
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.output.FileOutputFormat;
public class Co {
    public class Middle implements WritableComparable {
        public int number;
        public String page;
        Middle() {
            number = -1;
            page = "";
        }
        public void write(DataOutput out) throws IOException {
            out.writeInt(number);
            out.writeUTF(page);
        }
        public void readFields(DataInput in) throws IOException {
            number = in.readInt();
            page = in.readUTF();
        }
        public int compareTo(Middle o) {
            int thisValue = this.value;
            int thatValue = o.value;
            return (thisValue < thatValue ? -1 : (thisValue == thatValue ? 0 : 1));
        }
    }
    public static class TokenizerMapper extends Mapper<Object, Text, Text, Middle> {
        public void map(Object key, Text value, Context context) throws IOException, InterruptedException {
            Middle temp = new Middle();
            temp.page = "1";
            temp.number = 1;
            context.write(new Text("A"), temp);
        }
    }
    public static class IntSumReducer extends Reducer<Text, Middle, Text, DoubleWritable> {
        public void reduce(Text key, Iterable<Middle> values, Context context) throws IOException, InterruptedException {
            context.write(new Text("A"), new DoubleWritable(0.0));
        }
    }
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "word count");
        job.setJarByClass(Co.class);
        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(Mycombiner.class);
        job.setReducerClass(IntSumReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(Middle.class);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}

但是，由于我只是完全复制了参考资料中的代码，因此在编译程序时遇到了问题，下面是错误：

那么，谁能告诉我该怎么做？谢谢！