云计算-MapReduce
Hadoop示例程序WordCount详解及实例http://blog.csdn.net/xw13106209/article/details/6116323
hadoop中使用MapReduce编程实例（转）http://eric-gcm.iteye.com/blog/1807468
【mapreduce进阶编程二】奇偶行分别求和http://www.aboutyun.com/forum.php?mod=viewthread&tid=9360
hadoop2.2.0 MapReduce求和并排序http://www.cnblogs.com/mengyao/p/4151509.html
MapReduce求最大值http://blog.csdn.net/lzm1340458776/article/details/43227759
慢慢看！
求最大值：
import java.io.IOException;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
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.Partitioner;
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;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
public class Score2 {
private static String SPILT = " ";
private static int max = -10000;
public static class ScoreMapper extends Mapper<LongWritable, Text, Text, Text> {
public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
int num = Integer.valueOf(String.valueOf(value));
if (max < num)
max = num;
context.write(new Text(String.valueOf(max)), new Text(""));
}
}
public static class MaxReducer extends Reducer<Text, Text, Text, Text> {
@Override
public void reduce(Text key, Iterable<Text> value, Context context) throws IOException, InterruptedException {
int num = Integer.valueOf(String.valueOf(key));
if (num == max) {
context.write(new Text("max："), new Text(String.valueOf(num)));
}
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
String[] otherArgs = new GenericOptionsParser(conf, args).getRemainingArgs();
if (otherArgs.length < 2) {
System.out.println("please input at least 2 arguments");
System.exit(2);
}
Job job = Job.getInstance(conf, "max");
job.setJarByClass(Score2.class);
job.setMapperClass(ScoreMapper.class);
job.setReducerClass(MaxReducer.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(Text.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(Text.class);
job.setNumReduceTasks(1);
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
System.exit(job.waitForCompletion(true) ? 0 : 1);
}
}
import java.io.IOException;
import java.util.Iterator;
import java.util.StringTokenizer;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.DoubleWritable.Comparator;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.WritableComparable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Mapper.Context;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.util.GenericOptionsParser;
public class max {
public static class Map1 extends
Mapper<Object, Text, Text, IntWritable> {
public void map(Object key, Text value, Context context)
throws IOException, InterruptedException {
int count=0;
String line = value.toString();
String s[]=line.split(" ");
for (int i=0;i<s.length;i++)
{
//if (Integer.parseInt(s[i])<min)//s[i]bian int
//min=Integer.parseInt(s[i]);
char c[] = s[i].toCharArray();
if (c[c.length-1]=='h')
count++;
}
context.write(new Text("1"), new IntWritable(count));
//context.write(new Text(key.tostring),new IntWritable(max));
}
}
public static class Reduce1 extends
Reducer<Text, IntWritable, Text, IntWritable> {
public void reduce(Text key, Iterable<IntWritable> values,
Context context) throws IOException, InterruptedException {
//int min=1000000;
int sum=0;
Iterator<IntWritable> iterator = values.iterator(); //
while (iterator.hasNext()) {
int n=iterator.next().get();
// if (n<min)
// min=n;
sum=sum+n;
}
context.write(new Text(" "), new IntWritable(sum));
}
}
public static void main(String[] args) throws Exception {
Configuration conf = new Configuration();
FileSystem fs = FileSystem.get(conf);
conf.set("mapred.job.tracker", "127.0.0.1:9000");
String[] otherArgs = new GenericOptionsParser(conf, args)
.getRemainingArgs();
if (otherArgs.length != 2) { //input output
System.err.println("Usage: Data Deduplication <in> <out><out>");
System.exit(2);
}
Job job = Job.getInstance(conf,"min");
job.setJarByClass(max.class);
job.setMapperClass(Map1.class);
job.setMapOutputKeyClass(Text.class);
job.setMapOutputValueClass(IntWritable.class);
job.setReducerClass(Reduce1.class);
job.setOutputKeyClass(Text.class);
job.setOutputValueClass(IntWritable.class);
FileInputFormat.addInputPath(job, new Path(otherArgs[0]));
Path outpath = new Path(otherArgs[1]);
if (fs.exists(outpath))
{
fs.delete(outpath,true);
}
FileOutputFormat.setOutputPath(job, outpath);
if (job.waitForCompletion(true))
{
System.exit(0);
}
}
}
