Java - Parse string to its best match

Introduction

DateTimeFormatter class a parseBest() method parses string for its best match.

The following snippet of code specifies OffsetDateTime, LocalDateTime, and LocalDate as the preferred parsed result types:

String text = ...
TemporalAccessor ta = formatter.parseBest(text,
                                           OffsetDateTime::from,
                                           LocalDateTime::from,
                                           LocalDate::from);

The method will try to parse the text as the specified types in order and return the first successful result.

A call to the parseBest() method is followed by if-else statement with an instanceof operator to check what type of object was returned.

The following code shows how to use the parseBest() method.

Demo

import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.OffsetDateTime;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeParseException;
import java.time.temporal.TemporalAccessor;

public class Main {
  public static void main(String[] args) {
    DateTimeFormatter parser = DateTimeFormatter
        .ofPattern("yyyy-MM-dd['T'HH:mm:ss[Z]]");
    parseStr(parser, "2018-05-31");
    parseStr(parser, "2018-05-31T16:30:12");
    parseStr(parser, "2018-05-31T16:30:12-0500");
    parseStr(parser, "2018-05-31 wrong");
  }//from  w w  w.  j  ava 2s .  c  om

  public static void parseStr(DateTimeFormatter formatter, String text) {
    try {
      TemporalAccessor ta = formatter.parseBest(text, OffsetDateTime::from,
          LocalDateTime::from, LocalDate::from);
      if (ta instanceof OffsetDateTime) {
        OffsetDateTime odt = OffsetDateTime.from(ta);
        System.out.println("OffsetDateTime: " + odt);
      } else if (ta instanceof LocalDateTime) {
        LocalDateTime ldt = LocalDateTime.from(ta);
        System.out.println("LocalDateTime: " + ldt);
      } else if (ta instanceof LocalDate) {
        LocalDate ld = LocalDate.from(ta);
        System.out.println("LocalDate: " + ld);
      } else {
        System.out.println("Parsing returned: " + ta);
      }
    } catch (DateTimeParseException e) {
      System.out.println(e.getMessage());
    }
  }
}

Result

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