Map按照Value值进行排序
1 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 }}
输出结果
unsorted map: {D=67.3, A=99.5, B=67.4, C=67.4} results: {D=67.3, B=67.4, C=67.4, A=99.5}
2.HashMap按值进行排序
public class MapUtil{ public static <K, V extends Comparable<? super V>> Map<K, V> sortByValue( Map<K, V> map ) { List<Map.Entry<K, V>> list = new LinkedList<Map.Entry<K, V>>( map.entrySet() ); Collections.sort( list, new Comparator<Map.Entry<K, V>>() { public int compare( Map.Entry<K, V> o1, Map.Entry<K, V> o2 ) { return (o1.getValue()).compareTo( o2.getValue() ); } } ); Map<K, V> result = new LinkedHashMap<K, V>(); for (Map.Entry<K, V> entry : list) { result.put( entry.getKey(), entry.getValue() ); } return result; }}