hadoop--mapreduce--自定义key类型

问题：

输入文件A的样例如下（注意文件以tab为分隔符，粘贴时请检查）：

20170101 x

20170102 y

20170103 x

20170104 y

20170105 z

20170106 x

输入文件B的样例如下：

20170101 y

20170102 y

20170103 x

20170104 z

20170105 y

根据输入文件A和B合并得到的输出文件C的样例如下：

20170101 x

20170101 y

20170102 y

20170103 x

20170104 y

20170104 z

20170105 y 20170105 z

20170106 x

代码实现：

 1 import org.
apache.hadoop.fs.Path;
 2 import org.apache.hadoop.io.DoubleWritable;
 3 import org.apache.hadoop.io.IntWritable;
 4 import org.apache.hadoop.io.LongWritable;
 5 import org.apache.hadoop.io.Text;
 6 import org.apache.hadoop.mapreduce.Job;
 7 import org.apache.hadoop.mapreduce.Mapper;
 8 import org.apache.hadoop.mapreduce.Reducer;
 9 import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
10 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
11 import org.apache.hadoop.util.GenericOptionsParser;
12 
13 public class Task1 {
14     public static class MapClass extends Mapper<LongWritable, Text, Text, Text>{
15         public void map(LongWritable key,Text value,Context context) throws IOException, InterruptedException {
16             context.write(value, new Text(""));
17         }
18     }
19     public static  class ReduceClass extends Reducer<Text,Text,Text,Text>{
20         public void reduce( Text key, Iterable<Text> values,Context context) throws IOException, InterruptedException {
21             context.write(key, new Text(""));
22         }
23     }
24     public static void main(String args[]) throws IOException, ClassNotFoundException, InterruptedException {
25         Configuration conf = new Configuration();
26         Job job = new Job(conf);
27         job.setJarByClass(Task1.class);
28         job.setMapperClass(MapClass.class);
29         job.setReducerClass(ReduceClass.class);
30         job.setOutputKeyClass(Text.class);
31         job.setOutputValueClass(Text.class);
32         
33         FileInputFormat.addInputPath(job, new Path("C:\Users\Administrator\Desktop\新建文件夹\input2.txt")  );
34         FileInputFormat.addInputPath(job, new Path("C:\Users\Administrator\Desktop\\新建文件夹\input1.txt")  );
35         FileOutputFormat.setOutputPath(job, new Path("C:\Users\Administrator\Desktop\新建文件夹\output"));
36         
37         System.exit(job.waitForCompletion(true)?0:1);
38     }
39 }

结果：

踩过的坑：

　　reduce不执行的原因：

　　　　1、程序出现过异常，可以通过日志来debug；

　　　　2、参数类型不匹配；

　　　　等