Priority Queue add方法修改添加了最后一个元素的所有元素。为什么？

Question

/ 在hadoop reduce方法中，我将TopFrequency对象添加到PriorityQueue中。 假设我的reducer类中有getTotalCount方法。 totalCount是DoubleWritable类型的实例变量。 /

class TopFrequency{
    private double relativeFrequency;
    private WordPair wordPair;

    @Override
    public int compareTo(TopFrequency arg0){
        int i=this.wordPair.compareTo(arg0.wordPair);
        if(this.relativeCount<arg0.relativeCount){
           return -1;
        }else if(this.relativeCount>arg0.relativeCount){
            return 1;
        }else if(this.relativeCount==arg0.relativeCount){
            return 0;
        }
        return i;
    }
}
class WordPair{
    private Text word;
    private Text neighbor;
}
class Reduce extends Reducer{

@覆盖      protected void reduce（WordPair键，可迭代值，上下文上下文）{
            double rCount = 0.0;

        int count = getTotalCount(values);
        relativeFrequency=((double)count/totalCount.get());
        relativeCount.set((double) count / totalCount.get());

    //Creating an object of TopFrequency

        TopFrequency topFrequency=new TopFrequency(key, relativeFrequency);

    // All the references in reducerQueue point to   recently added object

        reducerQueue.add(topFrequency); 

       System.out.println("After adding to the queue "+reducerQueue);

    }
}