map reduce word count example doesn't work

Question

I try to implement the word count example by myself, here's my implementation of the mapper:

public static class Map extends Mapper<LongWritable, Text, Text, IntWritable> {

    public void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException {
        Text word = new Text();     
        String line = value.toString();
        StringTokenizer tokenizer = new StringTokenizer(line);
        while (tokenizer.hasMoreTokens()) {
            word.set(tokenizer.nextToken());
            context.write(word, new IntWritable(1));
        }
    }
}

and reducer:

public static class Reduce extends Reducer<Text, IntWritable, Text, IntWritable> {
    public void reduce(Text key, Iterator<IntWritable> values, Context context) throws IOException, InterruptedException {
        int sum = 0;
        while (values.hasNext())
            sum += values.next().get();
    context.write(key, new IntWritable(sum));
    }
}

but the output I get for executing this code looks like the output of mapper only, for example, if the input is "hello world hello", the output would be

hello 1
hello 1
world 1

I also use combiner between mapping and reducing. Can anyone explain me what's wrong with this code?

Thanks a lot!