Question

我正在尝试解析对包含大量数据（1000K）的地图进行排序。有没有比这更有效的方法来排序这些地图？下面是代码片段。

    Map<Integer, String> myMap1 = new HashMap<Integer, String>();
    Map<String,Integer>  myMap2 = new HashMap< String,Integer>();

    List <Entry<Integer,String>> lst1 = new ArrayList<Entry<Integer,String>>(myMap1.entrySet());
    Collections.sort(lst1, new Comparator<Entry<Integer,String>>(){
        @Override
        public int compare(Entry e1, Entry e2)
        {
            return ((String) e1.getValue()).compareTo((String) e2.getValue());
        }}
    );


    List <Entry<String,Integer>> lst2 = new ArrayList<Entry<String,Integer>>(myMap2.entrySet());        
    Collections.sort(lst2, new Comparator<Entry<String,Integer>>(){
        @Override
        public int compare(Entry e1, Entry e2)
        {
            return ((Integer) e1.getValue()).compareTo((Integer) e2.getValue());
        }}
    );

Answer 1

IMO优先级队列也是一种很好的方法：

Map<Integer, String> myMap1 = new HashMap<Integer, String>();
PriorityQueue<Entry<Integer, String>> pq = new PriorityQueue<Map.Entry<Integer,String>>(myMap1.size(), new Comparator<Entry<Integer, String>>() {
    @Override
    public int compare(Entry<Integer, String> arg0, Entry<Integer, String> arg1) {
        return arg0.getValue().compareTo(arg1.getValue());
    }
});
pq.addAll(myMap1.entrySet());
while (!pq.isEmpty()) {
    System.out.println(pq.poll());
}

Google Guava也是一个不错的选择，因为它提供了可以反转的BiMap实现，然后只对倒置的地图键进行排序。

 Map<Integer, String> myMap1 = new HashMap<Integer, String>();
    // insert values in myMap
    Map<String,Integer>  myMap2 = myMap1.inverse();
    SortedMap<Integer, Character> sortedInversed = new TreeMap<Integer, Character>(myMap2 );

Map <string，integer =“”>和Map <integer，string =“”>排序

1 个答案: