maxint.maxint.java Source code

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Here is the source code for maxint.maxint.java

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package maxint;
/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Last modified by: Andrey Danilkovich
 * Class: CS422 - Data mining
 * Illinois Institute of Technology
 * Max integer
 */

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.IntWritable;
import org.apache.hadoop.io.LongWritable;
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;
import org.apache.hadoop.util.GenericOptionsParser;

public class maxint {

    public static class TokenizerMapper extends Mapper<LongWritable, Text, Text, IntWritable> {

        // create new text with empty string
        private Text file = new Text("0");
        // make it writable with function
        private IntWritable number = new IntWritable();

        public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
            // read string line
            String line = value.toString();
            // set default max to 0
            int max = 0;
            // split the string by space separator
            String[] tokens = line.split(" ");
            // enter loop
            for (String token : tokens) {
                // parse the token
                int i = Integer.parseInt(token);
                if (i > max) {
                    max = i;
                }
            }
            number.set(max);
            String output = Integer.toString(max);
            //Text final_output = Text.set(output);
            Text final_output = new Text(output);
            // key-value pair: pass function with the key (file name) and max integer (result)
            context.write(file, number);
        }
    }

    /* test case - obscelete */
    public static class MaxIntReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
        private IntWritable result = new IntWritable();

        public void reduce(Text key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {
            int max = 0;
            for (IntWritable val : values) {
                int j = val.get();
                if (j > max) {
                    max = j;
                }
            }
            result.set(max);
            // key-value pair: pass function with the key and max integer
            // key-value pair: file name, max integer
            context.write(key, result);
        }
    }

    /* reduce function to compare the integers and collect the largest number from each file */
    public void reduce(K key, Iterator<V> values, Context context) throws IOException {
        //set v max to next value
        V max = values.next();
        // evaluate
        while (values.hasNext()) {
            // set to current value
            V current = values.next();
            // check if max, then override
            if (current.compareTo(max) > 0)
                max = current;
        }
        // key-value pair: pass function with the key and max integer
        context.collect(key, max);
    }

    /* main function */
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();
        String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
        if (otherArgs.length != 2) {
            System.err.println("Usage: max integer <in> <out>");
            System.exit(2);
        }
        Job job = new Job(conf, "max integer");
        job.setJarByClass(maxint.class);
        job.setMapperClass(TokenizerMapper.class);
        job.setCombinerClass(MaxIntReducer.class);
        job.setReducerClass(MaxIntReducer.class);
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);
        FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
        FileOutputFormat.setOutputPath(job, new Path(otherArgs[1]));
        System.exit(job.waitForCompletion(true) ? 0 : 1);
    }
}