How to Handle 'Illegal pattern character 'T'' When Parsing Dates in Java?

Parsing Date Strings with Illegal Character

When attempting to parse a date string in Java using SimpleDateFormat, you may encounter the exception "Illegal pattern character 'T'". This issue arises when the date string contains a 'T' character, which designates the time component when following the ISO 8601 standard.

Cause of the Exception

The SimpleDateFormat class interprets 'T' as a special character that separates the date and time portions of the string. However, the default pattern does not include 'T' as a character, leading to the exception.

Possible Solutions

There are several ways to address this issue:

1. Modify the Pattern:

   • Add a single quote on both sides of 'T' in the pattern string. This escapes the character, allowing it to be interpreted as a literal.
   • Example: SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'hh:mm:ssZ")

2. Use DateTimeFormatter (Java 8 ):

   • Start using the modern DateTimeFormatter class introduced in Java 8.
   • Create a formatter with appropriate date and time patterns.

   • Example:

      DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssZ");
      Date date = formatter.parse("2010-10-02T12:23:23Z", LocalDateTime::from);

3. Manual String Splitting:

   • If the above approaches do not work, consider splitting the date string manually and parsing the date and time components separately.

Note:

If the date string contains a trailing 'Z' to denote UTC time, ensure that the 'XXX' part of the pattern is included.

Improved Code Sample (with escaped 'T'):

public static void main(String[] args) {
    String date = "2010-10-02T12:23:23Z";
    String pattern = "yyyy-MM-dd'T'hh:mm:ssXXX";
    SimpleDateFormat sdf = new SimpleDateFormat(pattern);
    try {
        Date d = sdf.parse(date);
        System.out.println(d.getYear());
    } catch (ParseException e) {
        e.printStackTrace();
    }
}

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