Java Date issues

Question

Im having a problem with java date's, when i pass a date before 1949 into the bellow method. The date i have returned is for example 2049, im aware it has somthing to do with the date format and thought using yyyy instead of RRRR would have fixed it. But i just dont understand why or how to reslove it. Any help will be much apreciated

public static java.sql.Date parseDate(String date) throws ParseException {
  if (date != null) {
   SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yyyy");
   return new java.sql.Date(dateFormat.parse(date).getTime());
  }
  return null;
 }

Thanks Jon

Answer 1

let me format that for you..

public static java.sql.Date parseDate(String date) throws ParseException {
    if (date != null) { 
        SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MMM-yyyy"); 
        return new java.sql.Date(dateFormat.parse(date).getTime()); 
    } 
    return null; 
}

This I suspect is what you want...

private Date convertDate() throws ParseException
{
    String dateStr = "21-02-2010";
    SimpleDateFormat dateFormat = new SimpleDateFormat("dd-MM-yyyy");
    Date date = null;
    if (dateStr != null)
    {
      date = new Date(dateFormat.parse(dateStr).getTime());
    }

    System.out.println(date);
    return date;
}

For 21-02-2010 you will get... Sun Feb 21 00:00:00 GMT 2010

For 21-02-1938 you will get... Mon Feb 21 00:00:00 GMT 1938

Does that help? I might of been due to you having MMM in your code.

Answer 2

tl;dr

java.sql.Date.valueOf( 
    LocalDate.parse( "12-Jan-23" , DateTimeFormatter.ofPattern( "dd-MMM-uuuu" , Locale.US ) ) 
)

Time Zone

Your code ignores the crucial issue of time zone. Determining a date requires a time zone. For any given moment, the date varies around the globe by zone.

Your code uses Date which is always in UTC. So your date value produced from the misnamed Date class will be accurate for UTC but not valid for other time zones such as America/Montreal or Asia/Kolkata.

Using java.time

The modern way to do this work is with the java.time classes that supplant the troublesome old legacy date-time classes.

The LocalDate class represents a date-only value without time-of-day and without time zone.

To parse an incoming string, define a formatting pattern with DateTimeFormatter. Specify a Locale for the human language to be used in translating the name of the month.

DateTimeFormatter f = DateTimeFormatter.ofPattern( "dd-MMM-uuuu" , Locale.US );
LocalDate localDate = LocalDate.parse( "12-Jan-2017" , f );

With JDBC 4.2 and later, you can pass the LocalDate directly to your database with setObject and getObject methods.

For a JDBC driver not yet updated, fall back to the java.sql types.

java.sql.Date sqlDate = java.sql.Date.valueOf( localDate );
LocalDate localDate = sqlDate.toLocalDate();

---

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

Where to obtain the java.time classes?

• Java SE 8 and SE 9 and later
  • Built-in.
  • Part of the standard Java API with a bundled implementation.
  • Java 9 adds some minor features and fixes.
• Java SE 6 and SE 7
  • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • The ThreeTenABP project adapts ThreeTen-Backport (mentioned above) for Android specifically.
  • See How to use ThreeTenABP….

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.