定义DoubleArray并将其作为value写入SequenceFile

1)上代码：

 1 /**
 2  * Created with IntelliJ IDEA.
 3  * User: hadoop
 4  * Date: 16-1-20
 5  * Time: 下午7:30
 6  * To change this template use File | Settings | File Templates.
 7  */
 8 import org.apache.hadoop.io.*;
 9 import java.util.*;
10 public class DoubleWritableArray {
11     public static class DoubleArray extends ArrayWritable{
12       public DoubleArray(){
13           super(DoubleWritable.class);
14       }
15        // public  DoubleWritable[] get(){return values;}
16 
17 
18        public static double[] convert2double(DoubleWritable[] w){
19             double[] value=new double[w.length];
20             for (int i = 0; i < value.length; i++) {
21                 value[i]=Double.valueOf(w[i].get());
22             }
23             return value;
24         }
25 
26 
27     }
28 
29     public static void main(String[]args){
30 
31 
32         ArrayWritable aw=new ArrayWritable(DoubleWritable.class);
33         aw.set(new DoubleWritable[] {new DoubleWritable(4.34),new DoubleWritable(6.56),
34                 new DoubleWritable(9.56)});
35 
36         DoubleWritable[] values=(DoubleWritable[])aw.get();
37         for(DoubleWritable val1:values){
38             System.out.println(val1);
39         }
40         //与ArrayWritable相比，新定义的DoubleArray只是在调用构造函数的时候少写了DoubleWritable类而已
41         DoubleArray d=new DoubleArray();
42         d.set(new DoubleWritable[] {new DoubleWritable(4.34),new DoubleWritable(6.56),
43                 new DoubleWritable(9.56)});
44 
45         double[] temp=DoubleArray.convert2double((DoubleWritable[])d.get())   ;
46         for (double val:temp)
47             System.out.println(val);
48 
49 
50 
51     }
52 
53 
54 }

ArrayWritable作为reduce的输入的话，需要创建其子类，在子类中创建一个无参构造函数。

来源：http://grepcode.com/file/repo1.maven.org/maven2/org.jvnet.hudson.hadoop/hadoop-core/0.19.1-hudson-2/org/apache/hadoop/io/ArrayWritable.java#ArrayWritable.toArray%28%29

2）读取txt文件并将其以<long,DoubleArray>作为键值对的形式写入SequenceFile

 1 package convert;
 2 
 3 /**
 4  * Created with IntelliJ IDEA.
 5  * User: hadoop
 6  * Date: 16-1-19
 7  * Time: 下午3:09
 8  * To change this template use File | Settings | File Templates.
 9  */
10 import java.io.IOException;
11 import java.net.URI;
12 
13 import org.apache.hadoop.conf.Configuration;
14 import org.apache.hadoop.fs.FileSystem;
15 import org.apache.hadoop.fs.Path;
16 import org.apache.hadoop.io.DoubleWritable;
17 import org.apache.hadoop.io.IOUtils;
18 import org.apache.hadoop.io.IntWritable;
19 import org.apache.hadoop.io.LongWritable;
20 import org.apache.hadoop.io.SequenceFile;
21 import org.apache.hadoop.io.Text;
22 import org.apache.commons.io.FileUtils;
23 import org.apache.commons.io.LineIterator;
24 
25 
26 
27 //import Jama.Matrix.*;
28 //import  java.io.IOException;
29 import java.io.File;
30 
31 //import javax.sound.midi.SysexMessage;
32 public class SequenceFileWriteDemo {
33     public static void main(String[] args) throws IOException {
34         String uri ="/home/hadoop/srcData/bDoubleArraySeq";
35         Configuration conf = new Configuration();
36         FileSystem fs = FileSystem.get(URI.create(uri), conf);
37         Path path = new Path(uri);
38         LongWritable key = new LongWritable();
39         DoubleArrayWritable value = new DoubleArrayWritable();
40         SequenceFile.Writer writer = null;
41         try {
42             writer = SequenceFile.createWriter(fs, conf, path, key.getClass(),
43                     value.getClass());
44 
45 
46             final LineIterator it2 = FileUtils.lineIterator(new File("/home/hadoop/srcData/transB.txt"), "UTF-8");
47             try {
48                 int i=0;
49                 String[] strings;
50                 DoubleWritable[] ArrayDoubleWritables;
51                 while (it2.hasNext()) {
52                     ++i;
53                     final String line = it2.nextLine();
54                     key.set(i);
55                     strings=line.split("	");
56                     ArrayDoubleWritables=new DoubleWritable[strings.length];
57                     for (int j = 0; j < ArrayDoubleWritables.length; j++) {
58                         ArrayDoubleWritables[j] =new DoubleWritable(Double.valueOf(strings[j]));
59                         
60                     }
61                     
62                     value.set(ArrayDoubleWritables);
63                     writer.append(key,value);
64                     //System.out.println("ffd");
65 
66                 }
67             } finally {
68                 it2.close();
69             }
70 
71         }finally {
72             IOUtils.closeStream(writer);
73         }
74         System.out.println("ok");
75 
76     }
77 
78 }