TopPopularLinks.java

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.ArrayWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
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.KeyValueTextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;

import java.io.IOException;
import java.lang.Integer;
import java.util.StringTokenizer;
import java.util.TreeSet;

// >>> Don't Change
public class TopPopularLinks extends Configured implements Tool {
    public static final Log LOG = LogFactory.getLog(TopPopularLinks.class);

    public static void main(String[] args) throws Exception {
        int res = ToolRunner.run(new Configuration(), new TopPopularLinks(), args);
        System.exit(res);
    }

    public static class IntArrayWritable extends ArrayWritable {
        public IntArrayWritable() {
            super(IntWritable.class);
        }

        public IntArrayWritable(Integer[] numbers) {
            super(IntWritable.class);
            IntWritable[] ints = new IntWritable[numbers.length];
            for (int i = 0; i < numbers.length; i++) {
                ints[i] = new IntWritable(numbers[i]);
            }
            set(ints);
        }
    }
// <<< Don't Change

    @Override
    public int run(String[] args) throws Exception {
        // TODO
    }

    public static class LinkCountMap extends Mapper<Object, Text, IntWritable, IntWritable> {
        // TODO
    }

    public static class LinkCountReduce extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
        // TODO
    }

    public static class TopLinksMap extends Mapper<Text, Text, NullWritable, IntArrayWritable> {
        Integer N;

        @Override
        protected void setup(Context context) throws IOException,InterruptedException {
            Configuration conf = context.getConfiguration();
            this.N = conf.getInt("N", 10);
        }
        // TODO
    }

    public static class TopLinksReduce extends Reducer<NullWritable, IntArrayWritable, IntWritable, IntWritable> {
        Integer N;

        @Override
        protected void setup(Context context) throws IOException,InterruptedException {
            Configuration conf = context.getConfiguration();
            this.N = conf.getInt("N", 10);
        }
        // TODO
    }
}

// >>> Don't Change
class Pair<A extends Comparable<? super A>,
        B extends Comparable<? super B>>
        implements Comparable<Pair<A, B>> {

    public final A first;
    public final B second;

    public Pair(A first, B second) {
        this.first = first;
        this.second = second;
    }

    public static <A extends Comparable<? super A>,
            B extends Comparable<? super B>>
    Pair<A, B> of(A first, B second) {
        return new Pair<A, B>(first, second);
    }

    @Override
    public int compareTo(Pair<A, B> o) {
        int cmp = o == null ? 1 : (this.first).compareTo(o.first);
        return cmp == 0 ? (this.second).compareTo(o.second) : cmp;
    }

    @Override
    public int hashCode() {
        return 31 * hashcode(first) + hashcode(second);
    }

    private static int hashcode(Object o) {
        return o == null ? 0 : o.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (!(obj instanceof Pair))
            return false;
        if (this == obj)
            return true;
        return equal(first, ((Pair<?, ?>) obj).first)
                && equal(second, ((Pair<?, ?>) obj).second);
    }

    private boolean equal(Object o1, Object o2) {
        return o1 == o2 || (o1 != null && o1.equals(o2));
    }

    @Override
    public String toString() {
        return "(" + first + ", " + second + ')';
    }
}
// <<< Don't Change