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  1. /* package whatever; // don't place package name! */
  2.  
  3. import java.util.regex.*;
  4. import java.lang.*;
  5. import java.time.*;
  6. import java.time.format.*;
  7.  
  8. /* Name of the class has to be "Main" only if the class is public. */
  9. class Ideone
  10. {
  11. 	private static DateTimeFormatter DMY = new DateTimeFormatterBuilder()
  12.         .appendOptional(DateTimeFormatter.ofPattern("dd-MM[-uuuu]"))
  13.         .appendOptional(DateTimeFormatter.ofPattern("dd/MM[/uuuu]"))
  14.         .toFormatter().withResolverStyle(ResolverStyle.STRICT);
  15.         /* outra opção seria
  16.         new DateTimeFormatterBuilder()
  17.         .optionalStart()
  18.         .appendPattern("dd-MM[-uuuu]")
  19.         .optionalEnd()
  20.         .optionalStart()
  21.         .appendPattern("dd/MM[/uuuu]")
  22.         .optionalEnd()
  23.         .toFormatter().withResolverStyle(ResolverStyle.STRICT);
  24.         */
  25.     private static Pattern POSSIBLE_DATE_REGEX = Pattern.compile("\\b\\d{2}[-/]\\d{2}([-/]\\d{4})?\\b");
  26.  
  27.     static String getDate(String text) {
  28.         Matcher matcher = POSSIBLE_DATE_REGEX.matcher(text);
  29.         if (matcher.find()) { // se encontrou, valida a data
  30.             String possivelData = matcher.group();
  31.             try {
  32.                 DMY.parseBest(possivelData, LocalDate::from, MonthDay::from);
  33.             } catch (DateTimeParseException e) {
  34.                 // data inválida (se quiser, imprima o erro: System.out.println("Erro: " + e.getMessage());
  35.                 return null;
  36.             }
  37.             return possivelData;
  38.         }
  39.  
  40.         // se não encontrou, retorna null
  41.         return null;
  42.     }
  43.  
  44. 	public static void main (String[] args) throws java.lang.Exception
  45. 	{
  46.         final String text1 = "Foo bar foo bar foo bar 29/01/2021 foo bar foo bar";
  47.         final String text2 = "Foo bar foo bar 29-01-2021 foo bar foo bar";
  48.         final String text3 = "Foo bar foo bar 29/01 foo bar foo bar";
  49.         final String text4 = "Foo bar foo bar 29-01 foo bar foo bar";
  50.  
  51.         System.out.println(getDate(text1)); // 29/01/2021
  52.         System.out.println(getDate(text2)); // 29-01-2021
  53.         System.out.println(getDate(text3)); // 29/01
  54.         System.out.println(getDate(text4)); // 29-01
  55.         System.out.println(getDate("29.12"));
  56. 	}
  57. }
Success #stdin #stdout 0.12s 35344KB
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29/01/2021
29-01-2021
29/01
29-01
null
https://ideone.com/k69yHi
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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