0
我map.java类我试图通过这个错误:在地图显示java.lang.NullPointerException错误减少程序
context.write(新文本(stringWord),新文本(文件名))来发送文件名
recude.java
import java.io.IOException;
import org.apache.hadoop.io.*;
import org.apache.hadoop.mapreduce.*;
public class Reduce extends Reducer<Text, Text, Text, Text> {
@Override
public void reduce(Text key, Iterable<Text> values, Context context)
throws IOException, InterruptedException {
int sum = 0;
MapWritable occurenceInFile = new MapWritable();
for (Text val : values) {
if(occurenceInFile.containsKey(val)) {
occurenceInFile.put(val, new IntWritable(1));
} else {
IntWritable occurence = (IntWritable) occurenceInFile.get(val);
occurenceInFile.put(val, new IntWritable(occurence.get() + 1));
}
sum += 1;
}
String result = key.toString() + " (";
boolean flag = false;
for (Writable filenameWritable : occurenceInFile.keySet()) {
if (flag) {
result += ", ";
}
String filename = ((Text) filenameWritable).toString();
result += filename + "=" + ((IntWritable) occurenceInFile.get(filenameWritable)).toString();
flag = true;
}
result += ")\nTotal occurence of \"" + key + "\": " + Integer.toString(sum);
context.write(key, new Text(result));
}
}
错误代码此错误代码是显示在标准错误
Error: java.lang.NullPointerException
at Reduce.reduce(Reduce.java:18)
at Reduce.reduce(Reduce.java:6)
at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:180)
at org.apache.hadoop.mapred.ReduceTask.runNewReducer(ReduceTask.java:656)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:394)
at org.apache.hadoop.mapred.YarnChild$2.run(YarnChild.java:172)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.Subject.doAs(Subject.java:415)
at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1657)
at org.apache.hadoop.mapred.YarnChild.main(YarnChild.java:166)
我初学者n来编写一个wordcount程序,但我仍然不知道如何解决这个错误。
查看代码中的第6行和第18行。这是一个字数统计程序?看起来很乱。我确信有可能写一些更清洁的东西。 – duffymo
是的,这不是整个程序,但我认为在我的map.java和wordcount.java(主类) –
没有错误你认为是错误的。有一个错误。 JVM刚刚说清楚了。我相信这可以并且应该写得更清楚。在使用Hadoop进行尝试之前,我建议使用基于JDK8流的版本。如果你不能这么做,那么你很少有机会用大铁锤。先做一些简单的事情。 – duffymo