我需要HashMap根据存储在其中的值对我进行排序。在HashMap包含存储在手机联系人的名字。
HashMap
另外,我还要求在对值进行排序时对键进行自动排序,否则你可以说键和值绑定在一起,因此值的任何更改都应反映在键中。
HashMap<Integer,String> map = new HashMap<Integer,String>(); map.put(1,"froyo"); map.put(2,"abby"); map.put(3,"denver"); map.put(4,"frost"); map.put(5,"daisy");
要求的输出:
2,abby; 5,daisy; 3,denver; 4,frost; 1,froyo;
假设使用Java,则可以像下面这样对hashmap进行排序:
public LinkedHashMap<Integer, String> sortHashMapByValues( HashMap<Integer, String> passedMap) { List<Integer> mapKeys = new ArrayList<>(passedMap.keySet()); List<String> mapValues = new ArrayList<>(passedMap.values()); Collections.sort(mapValues); Collections.sort(mapKeys); LinkedHashMap<Integer, String> sortedMap = new LinkedHashMap<>(); Iterator<String> valueIt = mapValues.iterator(); while (valueIt.hasNext()) { String val = valueIt.next(); Iterator<Integer> keyIt = mapKeys.iterator(); while (keyIt.hasNext()) { Integer key = keyIt.next(); String comp1 = passedMap.get(key); String comp2 = val; if (comp1.equals(comp2)) { keyIt.remove(); sortedMap.put(key, val); break; } } } return sortedMap; }
只是一个开端的例子。这种方法在对HashMap进行排序并保留重复值的同时也更加有用。
尝试下面的代码对我来说很好。你可以选择升序和降序
import java.util.Collections; import java.util.Comparator; import java.util.HashMap; import java.util.LinkedHashMap; import java.util.LinkedList; import java.util.List; import java.util.Map; import java.util.Map.Entry; public class SortMapByValue { public static boolean ASC = true; public static boolean DESC = false; public static void main(String[] args) { // Creating dummy unsorted map Map<String, Integer> unsortMap = new HashMap<String, Integer>(); unsortMap.put("B", 55); unsortMap.put("A", 80); unsortMap.put("D", 20); unsortMap.put("C", 70); System.out.println("Before sorting......"); printMap(unsortMap); System.out.println("After sorting ascending order......"); Map<String, Integer> sortedMapAsc = sortByComparator(unsortMap, ASC); printMap(sortedMapAsc); System.out.println("After sorting descindeng order......"); Map<String, Integer> sortedMapDesc = sortByComparator(unsortMap, DESC); printMap(sortedMapDesc); } private static Map<String, Integer> sortByComparator(Map<String, Integer> unsortMap, final boolean order) { List<Entry<String, Integer>> list = new LinkedList<Entry<String, Integer>>(unsortMap.entrySet()); // Sorting the list based on values Collections.sort(list, new Comparator<Entry<String, Integer>>() { public int compare(Entry<String, Integer> o1, Entry<String, Integer> o2) { if (order) { return o1.getValue().compareTo(o2.getValue()); } else { return o2.getValue().compareTo(o1.getValue()); } } }); // Maintaining insertion order with the help of LinkedList Map<String, Integer> sortedMap = new LinkedHashMap<String, Integer>(); for (Entry<String, Integer> entry : list) { sortedMap.put(entry.getKey(), entry.getValue()); } return sortedMap; } public static void printMap(Map<String, Integer> map) { for (Entry<String, Integer> entry : map.entrySet()) { System.out.println("Key : " + entry.getKey() + " Value : "+ entry.getValue()); } } }
编辑:版本2
使用了新的Java功能,例如流for-each等
如果值相同,则地图将按键排序
import java.util.*; import java.util.Map.Entry; import java.util.stream.Collectors; public class SortMapByValue { private static boolean ASC = true; private static boolean DESC = false; public static void main(String[] args) { // Creating dummy unsorted map Map<String, Integer> unsortMap = new HashMap<>(); unsortMap.put("B", 55); unsortMap.put("A", 20); unsortMap.put("D", 20); unsortMap.put("C", 70); System.out.println("Before sorting......"); printMap(unsortMap); System.out.println("After sorting ascending order......"); Map<String, Integer> sortedMapAsc = sortByValue(unsortMap, ASC); printMap(sortedMapAsc); System.out.println("After sorting descending order......"); Map<String, Integer> sortedMapDesc = sortByValue(unsortMap, DESC); printMap(sortedMapDesc); } private static Map<String, Integer> sortByValue(Map<String, Integer> unsortMap, final boolean order) { List<Entry<String, Integer>> list = new LinkedList<>(unsortMap.entrySet()); // Sorting the list based on values list.sort((o1, o2) -> order ? o1.getValue().compareTo(o2.getValue()) == 0 ? o1.getKey().compareTo(o2.getKey()) : o1.getValue().compareTo(o2.getValue()) : o2.getValue().compareTo(o1.getValue()) == 0 ? o2.getKey().compareTo(o1.getKey()) : o2.getValue().compareTo(o1.getValue())); return list.stream().collect(Collectors.toMap(Entry::getKey, Entry::getValue, (a, b) -> b, LinkedHashMap::new)); } private static void printMap(Map<String, Integer> map) { map.forEach((key, value) -> System.out.println("Key : " + key + " Value : " + value)); } }