TreeMap按照value进行排序

public class Testing {  
  
    public static void main(String[] args) {  
  
        HashMap<String,Double> map = new HashMap<String,Double>();  
        ValueComparator bvc =  new ValueComparator(map);  
        TreeMap<String,Double> sorted_map = new TreeMap<String,Double>(bvc);  
  
        map.put("A",99.5);  
        map.put("B",67.4);  
        map.put("C",67.4);  
        map.put("D",67.3);  
  
        System.out.println("unsorted map: "+map);  
  
        sorted_map.putAll(map);  
  
        System.out.println("results: "+sorted_map);  
    }  
}  
  
class ValueComparator implements Comparator<String> {  
  
    Map<String, Double> base;  
    public ValueComparator(Map<String, Double> base) {  
        this.base = base;  
    }  
  
    // Note: this comparator imposes orderings that are inconsistent with equals.      
    public int compare(String a, String b) {  
        if (base.get(a) >= base.get(b)) {  
            return -1;  
        } else {  
            return 1;  
        } // returning 0 would merge keys  
    }  
}