MaxTemperature.java
package cn.kissoft.hadoop.week05;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
public class MaxTemperature {
public static void main(String[] args) throws Exception {
if (args.length != 2) {
System.err.println("Usage: MaxTemperature <input path> <output path>");
System.exit(-1);
}
Job job = new Job();
job.setJarByClass(MaxTemperature.class);
job.setJobName("Max temperature");
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(MaxTemperatureMapper.class);
job.setReducerClass(MaxTemperatureReducer.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
package cn.kissoft.hadoop.week05;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Mapper;
public class MaxTemperatureMapper extends Mapper<LongWritable, Text, Text, IntWritable> {
private static final int MISSING = 9999;
@Override
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String line = value.toString();
String year = line.substring(0, 4);
int airTemperature = Integer.parseInt(line.substring(13, 19).trim());
if (airTemperature != MISSING) {
context.write(new Text(year), new IntWritable(airTemperature));
}
}
}
package cn.kissoft.hadoop.week05;
import java.io.IOException;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;
public class MaxTemperatureReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
@Override
public void reduce(Text key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
int maxValue = Integer.MIN_VALUE;
for (IntWritable value : values) {
maxValue = Math.max(maxValue, value.get());
}
context.write(key, new IntWritable(maxValue));
}
}
[wukong@bd11 guide]$ hadoop jar pc.jar cn.kissoft.hadoop.week05.MaxTemperature ./ch02/1959.txt ./ch02/out/ Warning: $HADOOP_HOME is deprecated. 14/08/15 11:27:15 WARN mapred.JobClient: Use GenericOptionsParser for parsing the arguments. Applications should implement Tool for the same. 14/08/15 11:27:15 INFO input.FileInputFormat: Total input paths to process : 1 14/08/15 11:27:15 INFO util.NativeCodeLoader: Loaded the native-hadoop library 14/08/15 11:27:15 WARN snappy.LoadSnappy: Snappy native library not loaded 14/08/15 11:27:17 INFO mapred.JobClient: Running job: job_201408150916_0003 14/08/15 11:27:18 INFO mapred.JobClient: map 0% reduce 0% 14/08/15 11:27:31 INFO mapred.JobClient: map 100% reduce 0% 14/08/15 11:27:43 INFO mapred.JobClient: map 100% reduce 100% 14/08/15 11:27:46 INFO mapred.JobClient: Job complete: job_201408150916_0003 14/08/15 11:27:46 INFO mapred.JobClient: Counters: 29 14/08/15 11:27:46 INFO mapred.JobClient: Job Counters 14/08/15 11:27:46 INFO mapred.JobClient: Launched reduce tasks=1 14/08/15 11:27:46 INFO mapred.JobClient: SLOTS_MILLIS_MAPS=14494 14/08/15 11:27:46 INFO mapred.JobClient: Total time spent by all reduces waiting after reserving slots (ms)=0 14/08/15 11:27:46 INFO mapred.JobClient: Total time spent by all maps waiting after reserving slots (ms)=0 14/08/15 11:27:46 INFO mapred.JobClient: Launched map tasks=1 14/08/15 11:27:46 INFO mapred.JobClient: Data-local map tasks=1 14/08/15 11:27:46 INFO mapred.JobClient: SLOTS_MILLIS_REDUCES=12558 14/08/15 11:27:46 INFO mapred.JobClient: File Output Format Counters 14/08/15 11:27:46 INFO mapred.JobClient: Bytes Written=9 14/08/15 11:27:46 INFO mapred.JobClient: FileSystemCounters 14/08/15 11:27:46 INFO mapred.JobClient: FILE_BYTES_READ=9773826 14/08/15 11:27:46 INFO mapred.JobClient: HDFS_BYTES_READ=27544475 14/08/15 11:27:46 INFO mapred.JobClient: FILE_BYTES_WRITTEN=14776914 14/08/15 11:27:46 INFO mapred.JobClient: HDFS_BYTES_WRITTEN=9 14/08/15 11:27:46 INFO mapred.JobClient: File Input Format Counters 14/08/15 11:27:46 INFO mapred.JobClient: Bytes Read=27544368 14/08/15 11:27:46 INFO mapred.JobClient: Map-Reduce Framework 14/08/15 11:27:46 INFO mapred.JobClient: Map output materialized bytes=4886910 14/08/15 11:27:46 INFO mapred.JobClient: Map input records=444264 14/08/15 11:27:46 INFO mapred.JobClient: Reduce shuffle bytes=4886910 14/08/15 11:27:46 INFO mapred.JobClient: Spilled Records=1332792 14/08/15 11:27:46 INFO mapred.JobClient: Map output bytes=3998376 14/08/15 11:27:46 INFO mapred.JobClient: Total committed heap usage (bytes)=219496448 14/08/15 11:27:46 INFO mapred.JobClient: CPU time spent (ms)=6770 14/08/15 11:27:46 INFO mapred.JobClient: Combine input records=0 14/08/15 11:27:46 INFO mapred.JobClient: SPLIT_RAW_BYTES=107 14/08/15 11:27:46 INFO mapred.JobClient: Reduce input records=444264 14/08/15 11:27:46 INFO mapred.JobClient: Reduce input groups=1 14/08/15 11:27:46 INFO mapred.JobClient: Combine output records=0 14/08/15 11:27:46 INFO mapred.JobClient: Physical memory (bytes) snapshot=310345728 14/08/15 11:27:46 INFO mapred.JobClient: Reduce output records=1 14/08/15 11:27:46 INFO mapred.JobClient: Virtual memory (bytes) snapshot=1455665152 14/08/15 11:27:46 INFO mapred.JobClient: Map output records=444264 [wukong@bd11 guide]$ hadoop fs -ls ./ch02/out/ Warning: $HADOOP_HOME is deprecated. Found 3 items -rw-r--r-- 1 wukong supergroup 0 2014-08-15 11:27 /user/wukong/ch02/out/_SUCCESS drwxr-xr-x - wukong supergroup 0 2014-08-15 11:27 /user/wukong/ch02/out/_logs -rw-r--r-- 1 wukong supergroup 9 2014-08-15 11:27 /user/wukong/ch02/out/part-r-00000 [wukong@bd11 guide]$ hadoop fs -cat ./ch02/out/part-r-00000 Warning: $HADOOP_HOME is deprecated. 1959 418
MapReduce示例-气象站,布布扣,bubuko.com
原文：http://my.oschina.net/allman90/blog/301485