Project1

package org.apache.hadoop.ramapo;
import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
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.output.FileOutputFormat;

// Input-> utr.txt -> ut.csv -> uu.csv

// first step: output is <userId, likedMovieId> (where liked is 3.0 or greater)

public class Project{
  public static class MyMapper
        extends Mapper<LongWritable, Text, IntWritable, Text> {
            public void map (LongWritable key, Text value, Context context) throws IOException, InterruptedException{
              String[] lines = value.toString().split(",");
              Integer user = Integer.parseInt(lines[0]);
              Integer movie = Integer.parseInt(lines[1]);
              double rating = Double.parseDouble(lines[2]);

              context.write(new IntWritable(user), new Text(Integer.toString(movie) + "," + Double.toString(rating)));


            }
    }


  public static class MyReducer
        extends Reducer<IntWritable, Text, IntWritable, IntWritable> {
            public void reduce (IntWritable key, Iterable<Text> value, Context context) throws IOException, InterruptedException{

              for(Text val : value) {
                String[] lines = val.toString().split(",");
                Integer movie = Integer.parseInt(lines[0]);
                Double rating = Double.parseDouble(lines[1]);

                if (rating >= 3) {
                  System.out.println(key.toString() + " " + String.valueOf(rating));
                  context.write(key, new IntWritable(movie));
                }
              }
            }
    }

  public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        Job job = Job.getInstance(conf, "Project");
        job.setJarByClass(Project.class);
        job.setMapperClass(MyMapper.class);
        //job.setCombinerClass(MyReducer.class);
        job.setReducerClass(MyReducer.class);
        job.setMapOutputKeyClass(IntWritable.class);
        job.setMapOutputValueClass(Text.class);
        job.setOutputKeyClass(IntWritable.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
  }
}