MR-求每年最高气温
一、要求：求每年最高气温，原始数据如下：
2014010114 2014010216 2014010317 2014010410 2014010506 2012010609 2012010732 2012010812 2012010919 2012011023 2001010116 2001010212 2001010310 2001010411 2001010529 2013010619 2013010722 2013010812 2013010929 2013011023 2008010105 2008010216 2008010337 2008010414 2008010516 2007010619 2007010712 2007010812 2007010999 2007011023 2010010114 2010010216 2010010317 2010010410 2010010506 2015010649 2015010722 2015010812 2015010999 2015011023
二、源代码
TempMapper.java
package com.me.sy1; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; import java.io.IOException; public class TempMapper extends Mapper<LongWritable, Text,Text, IntWritable> { @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { Text out_ket = new Text(); IntWritable out_value = new IntWritable(); String line= value.toString(); String year=line.substring(0,4); int temperature=Integer.parseInt(line.substring(8)); out_ket.set(year); out_value.set(temperature); context.write(out_ket,out_value); } }
TempReduce.java
package com.me.sy1; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Reducer; import java.io.IOException; public class TempReducer extends Reducer<Text, IntWritable, Text, IntWritable> { @Override protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException { int maxValue = Integer.MIN_VALUE; StringBuffer sb = new StringBuffer(); //取values的最大值 for (IntWritable value : values) { maxValue = Math.max(maxValue, value.get()); sb.append(value).append(", "); } context.write(key, new IntWritable(maxValue)); } }