WordCount-JAVA版
WordCountMapper
import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; public class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> { Text k = new Text(); IntWritable v = new IntWritable(1); protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] words = line.split(" "); for (String word : words) { k.set(word); context.write(k, v); } } }
WordCountMapper
import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.LongWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Mapper; public class WordCountMapper extends Mapper<LongWritable, Text, Text, IntWritable> { Text k = new Text(); IntWritable v = new IntWritable(1); protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] words = line.split(" "); for (String word : words) { k.set(word); context.write(k, v); } } }
WordCountReducer
import java.io.IOException; import org.apache.hadoop.io.IntWritable; import org.apache.hadoop.io.Text; import org.apache.hadoop.mapreduce.Reducer; public class WordCountReducer extends Reducer<Text, IntWritable, Text, IntWritable>{ int sum; IntWritable v = new IntWritable(); @Override protected void reduce(Text key, Iterable<IntWritable> value, Context context) throws IOException, InterruptedException { // 1 累加求和 sum = 0; for (IntWritable count : value) { sum += count.get(); } // 2 输出 v.set(sum); context.write(key, v); } }