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  1. import java.time.*;
  2. import java.time.temporal.ChronoUnit;
  3. import java.util.*;
  4. import java.util.stream.*;
  5.  
  6. public class Main {
  7.     public static void main(String args[]) {
  8.         List<Item> items = Arrays.asList(
  9.             new Item(LocalDateTime.parse("2020-08-21T00:00:00"), LocalDateTime.parse("2020-08-21T00:02:00"), "item1"),
  10.             new Item(LocalDateTime.parse("2020-08-21T00:01:00"), LocalDateTime.parse("2020-08-21T00:03:00"), "item2"),
  11.             new Item(LocalDateTime.parse("2020-08-21T00:03:00"), LocalDateTime.parse("2020-08-21T00:07:00"), "item3"),
  12.             new Item(LocalDateTime.parse("2020-08-21T00:04:00"), LocalDateTime.parse("2020-08-21T00:12:00"), "item4"),
  13.             new Item(LocalDateTime.parse("2020-08-21T09:50:37"), LocalDateTime.parse("2020-08-21T09:56:49"), "item5"),
  14.             new Item(LocalDateTime.parse("2020-08-21T09:59:37"), LocalDateTime.parse("2020-08-21T10:02:37"), "item6"),
  15.             new Item(LocalDateTime.parse("2020-08-21T09:49:37"), LocalDateTime.parse("2020-08-21T09:51:37"), "item7"),
  16.             new Item(LocalDateTime.parse("2019-12-31T23:59:37"), LocalDateTime.parse("2020-01-01T00:03:37"), "item8"),
  17.             new Item(LocalDateTime.parse("2020-01-01T00:04:37"), LocalDateTime.parse("2020-01-01T00:06:37"), "item9"),
  18.             // added to test a single entry within 5 min range
  19.             new Item(LocalDateTime.parse("2020-01-01T00:42:37"), LocalDateTime.parse("2020-01-01T00:44:37"), "item10")
  20.         );
  21.  
  22.         items.stream()
  23.              .flatMap(Main::convert)
  24.              .collect(Collectors.groupingBy(x -> x.getKey(), LinkedHashMap::new, Collectors.mapping(x -> x.getValue(), Collectors.toList())))
  25.              .entrySet().stream()
  26.              .filter(x -> x.getValue().size() > 1)
  27.              .forEach(System.out::println);
  28.     }
  29.  
  30.     public static Stream<Map.Entry<String, Item>> convert(Item item) {
  31.         LocalDateTime start = getKey(item.getStartTime());
  32.         LocalDateTime end = getKey(item.getEndTime()).plusMinutes(5);
  33.  
  34.         return Stream
  35.                 .iterate(start, d -> d.plusMinutes(5))
  36.                 .limit(ChronoUnit.MINUTES.between(start, end) / 5)
  37.                 .map(d -> new AbstractMap.SimpleEntry(d + "**" + d.plusMinutes(5), item));
  38.     }
  39.  
  40.     public static LocalDateTime getKey(LocalDateTime time) {
  41.         return LocalDateTime.of(time.getYear(), time.getMonthValue(), time.getDayOfMonth(), time.getHour(), time.getMinute() - time.getMinute() % 5);
  42.     }
  43. }
  44.  
  45. class Item {
  46.     final LocalDateTime startTime;
  47.     final LocalDateTime endTime;
  48.     final String name;
  49.  
  50.     public Item(LocalDateTime s, LocalDateTime e, String n) {
  51.         startTime = s;
  52.         endTime = e;
  53.         name = n;
  54.     }
  55.  
  56.     public LocalDateTime getStartTime() {return startTime;}
  57.     public LocalDateTime getEndTime() {return endTime;}
  58.     public String getName() {return name;}
  59.     @Override
  60.     public String toString() {
  61.         return name;
  62.         //return "{ " + String.join(", ", name, startTime.toString(), endTime.toString()) + " }";
  63.     }
  64. }
Success #stdin #stdout 0.14s 38560KB
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stdin
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Standard input is empty
stdout
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2020-08-21T00:00**2020-08-21T00:05=[item1, item2, item3, item4]
2020-08-21T00:05**2020-08-21T00:10=[item3, item4]
2020-08-21T09:50**2020-08-21T09:55=[item5, item7]
2020-08-21T09:55**2020-08-21T10:00=[item5, item6]
2020-01-01T00:00**2020-01-01T00:05=[item8, item9]
https://ideone.com/irSgpJ
language:
Java (HotSpot 12)
created:
5 years ago
visibility:
public

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