環境：
Linux系統CentOS 6.3(64bit)
Hadoop1.1.2
Linux下Eclipse版本
最大值算法代碼：
package yunSave;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.conf.Configured;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.IntWritable;
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.input.TextInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat;
import org.apache.hadoop.util.Tool;
import org.apache.hadoop.util.ToolRunner;
//求最大值
public class MaxValue extends Configured implements Tool {
public static class MapClass extends Mapper<LongWritable, Text, IntWritable, IntWritable> {
private int maxNum = 0;
public void map(LongWritable key, Text value, Context context)
throws IOException, InterruptedException {
String[] str = value.toString().split(" ");
try {// 對於非數字字符我們忽略掉
for(int i=0;i<str.length;i++){
int temp = Integer.parseInt(str[i]);
if (temp > maxNum) {
maxNum = temp;
}
}
} catch (NumberFormatException e) {
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
context.write(new IntWritable(maxNum), new IntWritable(maxNum));
}
}
public static class Reduce extends Reducer<IntWritable, IntWritable, IntWritable, IntWritable> {
private int maxNum = 0;
public void reduce(IntWritable key, Iterable<IntWritable> values, Context context)
throws IOException, InterruptedException {
for (IntWritable val : values) {
if ( val.get() > maxNum) {
maxNum = val.get();
}
}
}
@Override
protected void cleanup(Context context) throws IOException,
InterruptedException {
context.write(new IntWritable(maxNum), new IntWritable(maxNum));
}
}
public int run(String[] args) throws Exception {
Configuration conf = getConf();
Job job = new Job(conf, "MaxNum");
job.setJarByClass(MaxValue.class);
FileInputFormat.setInputPaths(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setMapperClass(MapClass.class);
job.setCombinerClass(Reduce.class);
job.setReducerClass(Reduce.class);
job.setInputFormatClass(TextInputFormat.class);
job.setOutputFormatClass(TextOutputFormat.class);
job.setOutputKeyClass(IntWritable.class);
job.setOutputValueClass(IntWritable.class);
System.exit(job.waitForCompletion(true) ? 0 : 1);
return 0;
}
public static void main(String[] args) throws Exception {
long start = System.nanoTime();
int res = ToolRunner.run(new Configuration(), new MaxValue(), args);
System.out.println(System.nanoTime()-start);
System.exit(res);
}
}
輸入的文件內容：
[work@master ~]$ hadoop fs -cat input_20141107/555.txt
Warning: $HADOOP_HOME is deprecated.
1 5 10 9999
[work@master ~]$
[work@master ~]$ hadoop fs -cat input_20141107/666.txt
Warning: $HADOOP_HOME is deprecated.
111 222 333 888
[work@master ~]$
Eclipse的執行畫面：
1.Argument參數
program Arguments：
hdfs://master:9000/user/work/input_20141107 hdfs://master:9000/user/work/output_20141107
VM Arguments：
-Xms512m -Xmx1024m -XX:MaxPermSize=256m
點擊Run之後產生下面的結果
運行結果：
[work@master ~]$ hadoop fs -cat output_20141107/part-r-00000
Warning: $HADOOP_HOME is deprecated.
CentOS安裝和配置Hadoop2.2.0 http://www.linuxidc.com/Linux/2014-01/94685.htm
Ubuntu 13.04上搭建Hadoop環境 http://www.linuxidc.com/Linux/2013-06/86106.htm
Ubuntu 12.10 +Hadoop 1.2.1版本集群配置 http://www.linuxidc.com/Linux/2013-09/90600.htm
Ubuntu上搭建Hadoop環境（單機模式+偽分布模式） http://www.linuxidc.com/Linux/2013-01/77681.htm
Ubuntu下Hadoop環境的配置 http://www.linuxidc.com/Linux/2012-11/74539.htm
單機版搭建Hadoop環境圖文教程詳解 http://www.linuxidc.com/Linux/2012-02/53927.htm
搭建Hadoop環境（在Winodws環境下用虛擬機虛擬兩個Ubuntu系統進行搭建） http://www.linuxidc.com/Linux/2011-12/48894.htm
