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  1. import java.time.format.DateTimeFormatter;
  2. import java.time.format.DateTimeFormatterBuilder;
  3. import java.time.format.ResolverStyle;
  4. import java.time.temporal.ChronoField;
  5. import java.time.temporal.TemporalAccessor;
  6. import java.time.ZoneOffset;
  7. import java.time.LocalDate;
  8. import java.time.LocalDateTime;
  9. import java.time.ZonedDateTime;
  10. import java.time.OffsetDateTime;
  11.  
  12. class Ideone
  13. {
  14.     public static void main(String[] args) {
  15.     	try {
  16.         // Define the formatter with year as the first component, followed by month and day
  17.         DateTimeFormatterBuilder builder = new DateTimeFormatterBuilder()
  18.                 .appendPattern("yyyyMMdd"); // Year, Month, Day are now the base mandatory components
  19.  
  20.         // Make subsequent components optional
  21.         builder.optionalStart().appendPattern("HH").appendPattern("mm");
  22.         builder.optionalEnd(); // End of HHmm
  23.  
  24.         // Set default values for missing components to ensure successful parsing
  25.         // and to get a consistent result (e.g., start of day/month/year).
  26.         // Defaults for YEAR, MONTH, DAY are not strictly needed here since they are in the base pattern.
  27.         // However, if the base pattern itself could be optional (e.g., just "yyyy" then "MM" optional),
  28.         // these defaults would be critical.
  29.         builder.parseDefaulting(ChronoField.HOUR_OF_DAY, 0);
  30.         builder.parseDefaulting(ChronoField.MINUTE_OF_HOUR, 0);
  31.         builder.parseDefaulting(ChronoField.SECOND_OF_MINUTE, 0);
  32.         builder.parseDefaulting(ChronoField.NANO_OF_SECOND, 0); // Sets milliseconds to 0
  33.         builder.parseDefaulting(ChronoField.OFFSET_SECONDS, ZoneOffset.UTC.getTotalSeconds()); // Default to UTC offset
  34.  
  35.         DateTimeFormatter formatter = builder
  36.                 .toFormatter()
  37.                 .withResolverStyle(ResolverStyle.LENIENT); // Lenient for more forgiving parsing
  38.  
  39.         DateTimeFormatter formatterWithOffset = builder
  40.                 .toFormatter()
  41.                 .withResolverStyle(ResolverStyle.LENIENT);
  42.  
  43.         // --- Test cases ---
  44.         System.out.println("Parsing '20230101' (yyyyMMdd): " + formatter.parseBest("20230101", ZonedDateTime::from, LocalDateTime::from, LocalDate::from));
  45.         System.out.println("Parsing '20230115' (yyyyMMdd): " + formatter.parseBest("20230115", ZonedDateTime::from, LocalDateTime::from, LocalDate::from));
  46.         System.out.println("Parsing '202301151030' (yyyyMMddHHmm): " + formatter.parseBest("202301151030", ZonedDateTime::from, LocalDateTime::from, LocalDate::from));
  47.         System.out.println("Parsing '20230115103045' (yyyyMMddHHmmss): " + formatter.parseBest("20230115103045", ZonedDateTime::from, LocalDateTime::from, LocalDate::from));
  48.         System.out.println("Parsing '20230115103045123' (yyyyMMddHHmmssSSS): " + formatter.parseBest("20230115103045123", ZonedDateTime::from, LocalDateTime::from, LocalDate::from));
  49.  
  50.         System.out.println("Parsing '20230115103045123Z' (yyyyMMddHHmmssSSSZ): " + formatterWithOffset.parseBest("20230115103045123Z", ZonedDateTime::from, OffsetDateTime::from, LocalDateTime::from, LocalDate::from));
  51.         System.out.println("Parsing '20230115103045123+0500' (yyyyMMddHHmmssSSS+HHMM): " + formatterWithOffset.parseBest("20230115103045123+0500", ZonedDateTime::from, OffsetDateTime::from, LocalDateTime::from, LocalDate::from));
  52.         System.out.println("Parsing '20230115103045123-08' (yyyyMMddHHmmssSSS-HH): " + formatterWithOffset.parseBest("20230115103045123-08", ZonedDateTime::from, OffsetDateTime::from, LocalDateTime::from, LocalDate::from));
  53.     	} catch (Exception e) {
  54.     		System.out.println(e);
  55.     	}
  56.     }
  57. }
Success #stdin #stdout 0.16s 56688KB
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Standard input is empty
stdout
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Parsing '20230101' (yyyyMMdd): 2023-01-01T00:00Z
Parsing '20230115' (yyyyMMdd): 2023-01-15T00:00Z
java.time.format.DateTimeParseException: Text '202301151030' could not be parsed at index 0
https://ideone.com/qmxThw
language:
Java (HotSpot 12)
created:
1 day ago
visibility:
public

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