有关hadoop的问题"java.lang.RuntimeException:java.lang.ClassNotFoundException:"

这是我的源代码

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;
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.SequenceFileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.SequenceFileOutputFormat;
import org.apache.hadoop.util.GenericOptionsParser;

public class PageRank {

public static final String MAGIC_STRING = ">>>>";
boolean overwrite = true;

PageRank(boolean overwrite){
    this.overwrite = overwrite;
}
public static class TextPair implements WritableComparable{
    Text x;
    int ordering;

    public TextPair(){
        x = new Text();
        ordering = 1;
    }

    public void setText(Text t, int o){
        x = t;
        ordering = o;
    }

    public void setText(String t, int o){
        x.set(t);
        ordering = o;
    }


    public void readFields(DataInput in) throws IOException {
        x.readFields(in);
        ordering = in.readInt();
    }


    public void write(DataOutput out) throws IOException {
        x.write(out);
        out.writeInt(ordering);
    }


    public int hashCode() {
        return x.hashCode();
    }


    public int compareTo(TextPair o) {
        int x = this.x.compareTo(o.x);
        if(x==0)
            return ordering-o.ordering;
        else
            return x;
    }
}

public static class MapperA extends Mapper {

private Text word = new Text();
Text title = new Text();
Text link = new Text();
TextPair textpair = new TextPair();

boolean start=false;
String currentTitle="";
private Pattern linkPattern = Pattern.compile("\\[\\[\\s*(.+?)\\s*\\]\\]");
private Pattern titlePattern = Pattern.compile("");
private Pattern pagePattern = Pattern.compile("<page>\\s*(.+?)\\s*</page>");


public void map(LongWritable key, Text value,  Context context) throws IOException, InterruptedException {
    String line = value.toString();
    int startPage=line.lastIndexOf("