MapReduce Program - Finding The Average Age of Male and Female Died in Titanic Disaster

// Required imports for Hadoop MapReduce
import java.io.IOException;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.conf.*;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;

// Main class
public class Average_age {

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

        private Text gender = new Text();          // To store gender (Male/Female)
        private IntWritable age = new IntWritable();  // To store age value

        // Map method: runs for each line of input
        public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {

            String line = value.toString();        // Convert line to String
            String[] str = line.split(", ");       // Split line into fields using comma and space

            // Proceed only if sufficient columns are present
            if (str.length > 6) {
                gender.set(str[4]);                // 5th column = Gender

                if (str[1].equals("0")) {          // 2nd column = Survived (0 = Died)
                    if (str[5].matches("\\d+")) {  // 6th column = Age (only if numeric)
                        int i = Integer.parseInt(str[5]); // Convert age to integer
                        age.set(i);                // Set age as IntWritable
                        context.write(gender, age); // Emit (Gender, Age)
                    }
                }
            }
        }
    }

    // Reducer class
    public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {

        // Reduce method: receives all ages grouped by gender
        public void reduce(Text key, Iterable<IntWritable> values, Context context)
                throws IOException, InterruptedException {

            int sum = 0;       // Total age sum
            int count = 0;     // Count of records

            // Loop through all age values
            for (IntWritable val : values) {
                sum += val.get();   // Add age to sum
                count++;            // Increment count
            }

            int avg = sum / count;  // Calculate average age
            context.write(key, new IntWritable(avg)); // Emit (Gender, Average Age)
        }
    }

    // Driver/main method
    public static void main(String[] args) throws Exception {
        Configuration conf = new Configuration();                     // Create configuration
        Job job = new Job(conf, "Averageage_survived");              // Define job name

        job.setJarByClass(Average_age.class);                         // Set main class

        // Set output types for Mapper
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(IntWritable.class);

        // Set output types for Reducer
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(IntWritable.class);

        // Set Mapper and Reducer classes
        job.setMapperClass(Map.class);
        job.setReducerClass(Reduce.class);

        // Set input and output formats
        job.setInputFormatClass(TextInputFormat.class);
        job.setOutputFormatClass(TextOutputFormat.class);

        // Set input and output file paths from command line arguments
        FileInputFormat.addInputPath(job, new Path(args[0]));
        FileOutputFormat.setOutputPath(job, new Path(args[1]));

        // Optional: delete output path if it already exists
        Path out = new Path(args[1]);
        out.getFileSystem(conf).delete(out, true);

        // Run the job and wait for completion
        job.waitForCompletion(true);
    }
}