sorting by LocalDateTime in List<Model.Map<String, Object>> #LocalDateTime #List #sort #정렬

LocalDateTimeSorting.java

class LocalDateTimeSorting {
  
	public static void main (String... args) {
    
		List<Model> list = new ArrayList<>();

		Model m = new Model();
		Map<String, Object> map = new HashMap<>();

		map.put("datetime", "2019-07-08 18:10:10.0");

		m.setMapInfo(map);
      
      	list.add(m);
      
    	Model m2 = new Model();
		Map<String, Object> map2 = new HashMap<>();

		map2.put("datetime", "2019-07-04 18:10:10.0");

		m2.setMapInfo(map2);
      	list.add(m2);

		// add multiple Model in list
		// list.size() > 2

      	// list.sort need Comparator<? super E> c
      	// Comparator.comparing need 
      	//                 Function<? super T, ? extends U> keyExtractor,
        //                 Comparator<? super U> keyComparator
		list.sort(Comparator.comparing(
          		it -> (String) it.getExtraInfoValue("datetime"),
				(v1, v2) -> compare(v1, v2, "yyyy-MM-dd HH:mm:ss.S"))
        	);
      
      	System.out.println(m.getMapInfo.get("datetime")); // 2019-07-04 18:10:10.0

	}
  
	public static int compare(String value1, String value2, String format) {
		LocalDateTime d1 = LocalDateTime.parse(value1, DateTimeFormatter.ofPattern(format));
		LocalDateTime d2 = LocalDateTime.parse(value2, DateTimeFormatter.ofPattern(format));

		if (d1.isEqual(d2)) {
			return 0;
		}
		return d1.isAfter(d2) ? 1 : -1;
	}  
}