How Can I Efficiently Parse Dates with Multiple Formats Using SimpleDateFormat?

Parsing Dates in Varied Formats with SimpleDateFormat

When parsing dates from user input, it's common to encounter varying formats. Handling these variations can be challenging, especially considering the precedence rules of SimpleDateFormat.

To address this, use separate SimpleDateFormat objects for each unique format. Although this may seem to require excessive code duplication, the flexibility of SimpleDateFormat's number formatting rules allows for a more concise approach.

For instance, consider the following date formats:

• 9/09
• 9/2009
• 09/2009
• 9/1/2009
• 9-1-2009

These can be grouped into three categories:

• M/y (covering the first three)
• M/d/y (representing the fourth)
• M-d-y (for the fifth)

The following method exemplifies the implementation:

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;

public class DateParser {

  private static List<String> FORMAT_STRINGS = Arrays.asList("M/y", "M/d/y", "M-d-y");

  public static Date parse(String dateString) {
    for (String formatString : FORMAT_STRINGS) {
      try {
        return new SimpleDateFormat(formatString).parse(dateString);
      } catch (ParseException e) {
        // Ignore parse exceptions and continue to the next format
      }
    }

    return null; // If no formats match, return null
  }
}

In this way, you can handle a range of date formats without the need for excessive nested try/catch blocks or code duplication.

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