我的MapReducer不工作 - 无法获得输出

Question

public class SelfPatient {
    public static class selfMapper1 extends Mapper<LongWritable,Text,Text,IntWritable>
    {
        public void map(LongWritable key,Text value,Context context) throws IOException,InterruptedException
        {
            //IntWritable clas =new IntWritable(Integer.parseInt(str.nextToken(",")));
            String Line=value.toString();
            String[] elements=Line.split(",");
            int surv=Integer.parseInt(elements[1]);
            Text clas=new Text(elements[4]);
            //int i=Integer.parseInt(elements[0]);
            //IntWritable number=new IntWritable(i);
            context.write(new Text(clas),new IntWritable(surv));
            //context.write(clas,number);
        }
    }
    public static class selfReducer1 extends Reducer<Text,IntWritable,Text,IntWritable>
    {
        public void reduce(Text key,Iterable<IntWritable> values,Context context) throws IOException,InterruptedException
        {
            int sum=0;
            for (IntWritable val :values) 
            {
                sum += val.get();
            }
            context.write(key, new IntWritable(sum));
        }
    }

数据

"","survive","cases","age","sex","class"
"1",1,1,0,0,1
"2",13,13,0,0,2
"3",14,31,0,0,3
"4",5,5,0,1,1
"5",11,11,0,1,2
"6",13,48,0,1,3
"7",140,144,1,0,1
"8",80,93,1,0,2
"9",76,165,1,0,3
"10",57,175,1,1,1
"11",14,168,1,1,2
"12",75,462,1,1,3

我想得到的输出是：每个班级的幸存者总数。示例类 1-45、类 2-34。 我的代码有什么问题。

Answer 1

我假设您的"类"是逗号分隔数据中的最后一个数字。如果是这种情况，则您错误地将错误的值分配为键。

    String Line=value.toString();
    String[] elements=Line.split(",");
    int surv=Integer.parseInt(elements[1]);
    Text clas=new Text(elements[5]); //instead of elements[4]

发出映射器输出时，不必初始化新的 Text 对象，因为您之前已经这样做了。

    context.write(clas, new IntWritable(surv));

这应该可以解决您的问题。干杯。