import java.io.IOException;
import java.net.URI;
import java.util.Arrays;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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;
/**
* 作业:求最大的100个值
*
*/
public class top100 {
static final String INPUT = "hdfs://192.168.56.100:9000/input";
static final String OUT = "hdfs://192.168.56.100:9000/out";
static final Path INPUT_PATH = new Path(INPUT);
static final Path OUT_PATH = new Path(OUT);
static final int topNum = 100;
public static void main(String[] args) throws Exception{
Configuration conf = new Configuration();
FileSystem fileSystem = FileSystem.get(new URI(OUT),conf);
if(fileSystem.exists(OUT_PATH)){
fileSystem.delete(OUT_PATH,true);
}
Job job = new Job(conf,top100
.class.getSimpleName());
FileInputFormat.setInputPaths(job, INPUT_PATH);
job.setMapperClass(MyMapper.class);
job.setReducerClass(MyReducer.class);
job.setOutputKeyClass(LongWritable.class);
job.setOutputValueClass(NullWritable.class);
FileOutputFormat.setOutputPath(job, OUT_PATH);
job.waitForCompletion(true);
}
static class MyMapper extends Mapper<LongWritable, Text, LongWritable, NullWritable>{
@Override
protected void map(
LongWritable key,
Text value,
Mapper<LongWritable, Text, LongWritable, NullWritable>.Context context)
throws IOException, InterruptedException {
context.write(new LongWritable(Long.parseLong(value.toString())), NullWritable.get());
}
}
static class MyReducer extends Reducer<LongWritable, NullWritable, LongWritable, NullWritable>{
long[] topArray = new long[topNum];
int count = 0;
@Override
protected void reduce(
LongWritable k2,
Iterable<NullWritable> v2s,
Reducer<LongWritable, NullWritable, LongWritable, NullWritable>.Context context)
throws IOException, InterruptedException {
long num = Long.parseLong(k2.toString());
if(count < topNum){
topArray[count] = num;
count++;
}else{
Arrays.sort(topArray);
if(num > topArray[0]){
topArray[0] = num;
}
}
}
@Override
protected void cleanup(
Reducer<LongWritable, NullWritable, LongWritable, NullWritable>.Context context)
throws IOException, InterruptedException {
Arrays.sort(topArray);
for(int i = topArray.length -1 ; i > -1 ; i--){
context.write(new LongWritable(topArray[i]), NullWritable.get());
}
}
}
}
dashu
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