以下是使用MapReduce编程实现Top10操作的map与reduce方法中的一段代码，即提取最大的10个数，并正序（升序）输出。请填写空缺处的代码，运算符左右两侧不需要空格，比如a+b，而不是a + b；同时要注意单词大小写。

map输出键值对：(NullWritable, IntWritable)

public static class Top10Mapper extends Mapper<LongWritable, Text, NullWritable, IntWritable> {
    private TreeSet<Integer> top10 = new TreeSet<Integer>();
    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        String line = value.toString();
        Integer num = Integer.parseInt(line);
        top10.add(num);
        if (top10.size() > 10) {
            top10.remove(top10.first());
        }
    }
    protected void cleanup(Context context) throws IOException, InterruptedException {
        for (Integer num : top10) {
            context.write(NullWritable.get(), new IntWritable(num));
        }
    }
}

public static class Top10Reducer extends Reducer<NullWritable, IntWritable, NullWritable, IntWritable> {
    private TreeSet<Integer> top10 = new TreeSet<Integer>();
    public void reduce(NullWritable key, Iterable<IntWritable> values, Context context) throws IOException, InterruptedException {
        for (IntWritable value : values) {
            top10.add(value.get());
            if (top10.size() > 10) {
                top10.remove(top10.first());
            }
        }
        for (Integer num : top10) {
            context.write(NullWritable.get(), new IntWritable(num));
        }
    }
}

reduce输出键值对：(NullWritable, IntWritable)