Java tutorial
/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package crimesbyblockbymonth; import java.io.IOException; import java.util.Iterator; import java.util.StringTokenizer; import java.util.regex.Matcher; import java.util.regex.Pattern; import org.apache.hadoop.conf.Configuration; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.fs.Path; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapred.FileInputFormat; import org.apache.hadoop.mapred.FileOutputFormat; import org.apache.hadoop.mapred.JobClient; import org.apache.hadoop.mapred.JobConf; import org.apache.hadoop.mapred.KeyValueTextInputFormat; import org.apache.hadoop.mapred.MapReduceBase; import org.apache.hadoop.mapred.Mapper; import org.apache.hadoop.mapred.OutputCollector; import org.apache.hadoop.mapred.Reducer; import org.apache.hadoop.mapred.Reporter; import org.apache.hadoop.mapred.TextOutputFormat; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; /** * * @author Sattya */ public class CrimesByBlockByMonth extends Configured implements Tool { public static class MapClass extends MapReduceBase implements Mapper<Text, Text, Text, IntWritable> { private static final IntWritable one = new IntWritable(1); private Text word = new Text(); private String blockName = "100XX W OHARE ST"; public void map(Text key, Text value, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException { String line = key.toString(); if (line != null) { String[] cols = line.split(","); try { if (cols[3].equals(blockName)) { String date = cols[2]; Pattern p = Pattern.compile("(\\d*)/(\\d*)/(\\d*)\\s*(\\d*):(\\d*)"); Matcher m = p.matcher(date); if (m.find()) { String month = getMonth(m.group(1)); String year = "20" + m.group(3); word.set(year + "_" + month); output.collect(word, one); } } } catch (Exception e) { System.out.println("Bad row: " + e); } } } public String getMonth(String month) { switch (month) { case "1": return "Jan"; case "01": return "Jan"; case "2": return "Feb"; case "02": return "Feb"; case "3": return "Mar"; case "03": return "Mar"; case "4": return "Apr"; case "04": return "Apr"; case "5": return "May"; case "05": return "May"; case "6": return "Jun"; case "06": return "Jun"; case "7": return "Jul"; case "07": return "Jul"; case "8": return "Aug"; case "08": return "Aug"; case "9": return "Sep"; case "09": return "Sep"; case "10": return "Oct"; case "11": return "Nov"; case "12": return "Dec"; default: return "Invalid month"; } } } public static class Reduce extends MapReduceBase implements Reducer<Text, IntWritable, Text, IntWritable> { public void reduce(Text key, Iterator<IntWritable> values, OutputCollector<Text, IntWritable> output, Reporter reporter) throws IOException { int sum = 0; while (values.hasNext()) { sum += ((IntWritable) values.next()).get(); } output.collect(key, new IntWritable(sum)); } } public int run(String[] args) throws Exception { Configuration conf = getConf(); JobConf job = new JobConf(conf, CrimesByBlockByMonth.class); Path in = new Path(args[0]); Path out = new Path(args[1]); FileInputFormat.setInputPaths(job, in); FileOutputFormat.setOutputPath(job, out); job.setJobName("CrimesByBlockByMonth"); job.setMapperClass(MapClass.class); job.setReducerClass(Reduce.class); job.setInputFormat(KeyValueTextInputFormat.class); job.setOutputFormat(TextOutputFormat.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(IntWritable.class); // job.set("key.value.separator.in.input.line", ""); JobClient.runJob(job); return 0; } public static void main(String[] args) throws Exception { int res = ToolRunner.run(new Configuration(), new CrimesByBlockByMonth(), args); System.exit(res); } }