Hadoop最大值整数算法详解

╰半橙微兮° 2022-08-13 18:37 99阅读 0赞

环境：

Linux系统centOS6.3(64bit)

hadoop1.1.2

Linux下Eclipse版本

![Image 1][]

最大值算法代码：

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 \{// 对于非数字字符我们忽略掉  
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);    
\}    
\}

输入的文件内容：

\[work@master ~\]$ 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的执行画面：**

**1.Argument参数**

**program Arguments：**

**hdfs://master:9000/user/work/input\_20141107  hdfs://master:9000/user/work/output\_20141107**

**VM Arguments：**

**-Xms512m -Xmx1024m -XX:MaxPermSize=256m**

![Image 1][]

点击Run之后产生下面的结果

运行结果：