Code snippet from Hadoop Guide

Maximum.java

import org.apache.hadoop.hive.ql.exec.UDAF;
import org.apache.hadoop.hive.ql.exec.UDAFEvaluator;
import org.apache.hadoop.io.IntWritable;

public class Maximum extends UDAF {

public static class MaximumIntUDAFEvaluator implements UDAFEvaluator {

private IntWritable result;

         public void init() {
         result = null;
         }
        
         public boolean iterate(IntWritable value) {
         if (value == null) {
         return true;
         }
         if (result == null) {
         result = new IntWritable(value.get());
         } else {
         result.set(Math.max(result.get(), value.get()));
         }
         return true;
         }
         
         public IntWritable terminatePartial() {
         return result;
         }
         
         public boolean merge(IntWritable other) {
         return iterate(other);
         }
                 
         public IntWritable terminate() {
         return result;
         }
    }
}