排序地图条目
从 Java 8 开始,Map.Entry
接口上有默认方法,允许对地图迭代进行排序。
Version >= Java SE 8
Map<String, Integer> numberOfEmployees = new HashMap<>();
numberOfEmployees.put("executives", 10);
numberOfEmployees.put("human ressources", 32);
numberOfEmployees.put("accounting", 12);
numberOfEmployees.put("IT", 100);
// Output the smallest departement in terms of number of employees
numberOfEmployees.entrySet().stream()
.sorted(Map.Entry.comparingByValue())
.limit(1)
.forEach(System.out::println); // outputs : executives=10
当然,这些也可以在流 api 之外使用:
Version >= Java SE 8
List<Map.Entry<String, Integer>> entries = new ArrayList<>(numberOfEmployees.entrySet());
Collections.sort(entries, Map.Entry.comparingByValue());