Java8-對map排序

1、Java8對map按key排序

/**
 * @author : fengkun
 * @date : 19-3-10
 * 內容 ： Java8對map按key排序
 */
public class SortByKeyExample {

    public static void main(String[] args) {
        Map<String, Integer> unsortMap = new HashMap<>();
        unsortMap.put("z", 10);
        unsortMap.put("b", 5);
        unsortMap.put("a", 6);
        unsortMap.put("c", 20);
        unsortMap.put("d", 1);
        unsortMap.put("e", 7);
        unsortMap.put("y", 8);
        unsortMap.put("n", 99);
        unsortMap.put("g", 50);
        unsortMap.put("m", 2);
        unsortMap.put("f", 9);
        System.out.println(unsortMap);

        Map<String, Integer> result1 = unsortMap.entrySet().stream()
                .sorted(Map.Entry.comparingByKey())
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
                        (oleValue, newValue) -> oleValue, LinkedHashMap::new));
        System.out.println(result1);

        Map<String, Integer> result2 = new LinkedHashMap<>();
        unsortMap.entrySet().stream()
                .sorted(Map.Entry.comparingByKey())
                .forEachOrdered(x -> result2.put(x.getKey(), x.getValue()));
        System.out.println(result2);
    }
}

 

2、Java8對map按Vaule排序

/**
 * @author : fengkun
 * @date : 19-3-10
 * 內容 ： Java8對map按Vaule排序
 */
public class SoryByKeyExample {

    public static void main(String[] args) {
        Map<String, Integer> unsortMap = new HashMap<>();
        unsortMap.put("z", 10);
        unsortMap.put("b", 5);
        unsortMap.put("a", 6);
        unsortMap.put("c", 20);
        unsortMap.put("d", 1);
        unsortMap.put("e", 7);
        unsortMap.put("y", 8);
        unsortMap.put("n", 99);
        unsortMap.put("g", 50);
        unsortMap.put("m", 2);
        unsortMap.put("f", 9);
        System.out.println(unsortMap);

        Map<String, Integer> result1 = unsortMap.entrySet().stream()
                .sorted(Map.Entry.comparingByValue(Comparator.reverseOrder()))
                .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue,
                        (oldValue, newValue) -> oldValue, LinkedHashMap::new));

        System.out.println(result1);

        Map<String, Integer> result2 = new LinkedHashMap<>();
        unsortMap.entrySet().stream()
                .sorted(Map.Entry.<String, Integer>comparingByValue().reversed())
                .forEachOrdered(x -> result2.put(x.getKey(), x.getValue()));
        System.out.println(result2);
    }
}