com.bark.hadoop.lab3.PageRankReducer.java Source code

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Here is the source code for com.bark.hadoop.lab3.PageRankReducer.java

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/*
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package com.bark.hadoop.lab3;

import java.io.IOException;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

public class PageRankReducer extends Reducer<Text, Text, Text, Text> {

    @Override
    public void reduce(Text key, Iterable<Text> values, Context context) throws IOException, InterruptedException {
        double newPageRank = 0;
        /**
         * Pattern to distinguish our inserted numbers from numbers in titles
         * is: _!(numbers.numbers)
         */
        Pattern pt = Pattern.compile("(_!\\d+.\\S+)");
        String outGraph = "";
        for (Text t : values) {
            String s = t.toString();
            String[] ss = s.split(" ");
            /**
             * If value has more than 1 element, those are outLinks, keep them
             */
            if (ss.length > 1) {
                for (int i = 1; i < ss.length; i++) {
                    outGraph += " " + ss[i];
                }
            }
            /**
             * Read pageRanks and sum them up
             */
            Matcher mt = pt.matcher(s);
            if (mt.find()) {
                newPageRank += Double.parseDouble(mt.group(1).substring(2));
            }
        }
        //make sure not to include extra spaces (specially if outgraph is empty).
        //_!0.0000-space-A-space-B-space-C
        //_!0.0000-no space-
        context.write(key, new Text(("_!" + newPageRank + " " + outGraph.trim()).trim()));
    }
}