對HashMap中的值進行排序

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", 98.5);
	map.put("B", 85.0);
	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
}