如何在MapReduce作业中调用Reducer类，以便从reducer输出中不会返回重复的键？

import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;
import java.util.HashSet;
import java.util.Set;

public class MyReducer extends Reducer<Text, IntWritable, Text, IntWritable> {
    private Set<Text> processedKeys;

    @Override
    protected void setup(Context context) throws IOException, InterruptedException {
        processedKeys = new HashSet<>();
    }

    @Override
    protected void reduce(Text key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        // 检查键是否已经处理过
        if (!processedKeys.contains(key)) {
            int sum = 0;
            for (IntWritable value : values) {
                sum += value.get();
            }
            context.write(key, new IntWritable(sum));
            processedKeys.add(key);
        }
    }
}