根据日志信息，发现Map阶段的输出记录数为0，Reduce阶段的输入记录数也为0，可能是Mapper1类中的逻辑有问题。我对代码进行了修改，并添加了一些注释来帮助你理解：
import java.io.IOException;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.fs.Path;import org.apache.hadoop.io.IntWritable;import org.apache.hadoop.io.LongWritable;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.output.FileOutputFormat;public class Task1 {public static void main(String[] args) throws Exception {Configuration conf = new Configuration();Job job = Job.getInstance(conf, "task1");job.setJarByClass(Task1.class);job.setMapperClass(Mapper1.class);job.setReducerClass(Reducer1.class);// 设置Mapper和Reducer的输出类型job.setMapOutputKeyClass(Text.class);job.setMapOutputValueClass(IntWritable.class);job.setOutputKeyClass(Text.class);job.setOutputValueClass(IntWritable.class);// 修改输入路径和输出路径FileInputFormat.addInputPath(job, new Path("/exam/20560640321/train.csv"));FileOutputFormat.setOutputPath(job, new Path("/output/task1"));System.exit(job.waitForCompletion(true) ? 0 : 1);}public static class Mapper1 extends Mapper<LongWritable, Text, Text, IntWritable> {@Overridepublic void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {String line = value.toString();// 如果读入的是文件头，则直接跳过if (line.startsWith("instant")) {return;}String[] fields = line.split(",");if (fields.length < 2) {return;}String datetimeStr = fields[1];int count = Integer.parseInt(fields[10]);// 提取月份String[] datetimeParts = datetimeStr.split(" ");String[] dateParts = datetimeParts[0].split("/");String month = dateParts[1];// 输出<month, count>context.write(new Text(month), new IntWritable(count));}}public static class Reducer1 extends Reducer<Text, IntWritable, Text, IntWritable> {@Overridepublic void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {int sum = 0;// 计算同一月份的总计数值for (IntWritable value : values) {sum += value.get();}// 输出<month, total_count>context.write(key, new IntWritable(sum));}}}
修改后的代码中，我使用了LongWritable类型作为Mapper类的输入键类型，同时在map方法中进行了一些处理，避免输出不合法的记录。我还修改了输入路径和输出路径，并添加了更多注释帮助你理解程序运行逻辑。
