Java 8格式化日期输入

Question

I use this code to format a formatted text field to enter month & day:

SimpleDateFormat sdf = new SimpleDateFormat("MM.dd");
DateFormatter df = new DateFormatter(sdf);
DefaultFormatterFactory ddf = new DefaultFormatterFactory(df, df, df, df);
datumTextField.setValue(new Date(System.currentTimeMillis()));
datumTextField.setFormatterFactory(ddf);

When an invalid date is entered, eg. 13.10, a magican changes it to 1.10 after this line:

DateOfAdding = datumTextField.getText();

so the DateOfAddig value is 1.10.

How to turm the magican off?

Answer 1

tl;dr

MonthDay.parse( 
    "12.31" , 
     DateTimeFormatter.ofPattern( "MM.dd" ) 
)

Catch DateTimeParseException for invalid input.

java.time.MonthDay

The modern approach uses the java.time classes rather than the troublesome legacy classes seen in the Question.

Among the java.time classes is MonthDay , just what you need.

I suggest collecting input as two different numbers.

MonthDay md = MonthDay.of( x , y ) ;

If you insist, you can collect input as a combined string and parse . If so I suggest you and your user use standard ISO 8601 format: --MM-DD .

MonthDay md = MonthDay.parse( "--12-31" ) ;

Or define a pattern using DateTimeFormatter .

DateTimeFormatter f = DateTimeFormatter.ofPattern( "MM.dd" ) ;
MonthDay md = MonthDay.parse( input , f ) ;

Trap for DateTimeParseException to detect invalid inputs.

String input = "13.10" ;  // Invalid input. Month must be 1-12.
DateTimeFormatter f = DateTimeFormatter.ofPattern( "MM.dd" ) ;
MonthDay md = null ;
try 
{
    md = MonthDay.parse( input , f ) ;
} catch ( DateTimeParseException e ) { 
    // … handle error …
    System.out.println( "Invalid input: " + input ) ;
} 

See this code run live at IdeOne.com .

Invalid input: 13.10

e: java.time.format.DateTimeParseException: Text '13.10' could not be parsed: Unable to obtain MonthDay from TemporalAccessor: {MonthOfYear=13, DayOfMonth=10},ISO of type java.time.format.Parsed

md.toString(): null

Answer 2

You will want to call the SimpleDateFormat 's setLenient method with false as a parameter so that the underlying Calendar used for parsing is set to non-lenient.

A non-lenient calendar will refuse field values that aren't in the expected range for this field, rather than accepting them and modifying other fields to make sense of them : in your case the month was rolled-over 12 and reached 1, while the year was increased by 1 and probably reached 1971 rather than the default-when-unspecified 1970.

From the Calendar 's javadoc :

Leniency

Calendar has two modes for interpreting the calendar fields, lenient and non-lenient. When a Calendar is in lenient mode, it accepts a wider range of calendar field values than it produces. When a Calendar recomputes calendar field values for return by get(), all of the calendar fields are normalized. For example, a lenient GregorianCalendar interprets MONTH == JANUARY, DAY_OF_MONTH == 32 as February 1.

When a Calendar is in non-lenient mode, it throws an exception if there is any inconsistency in its calendar fields. For example, a GregorianCalendar always produces DAY_OF_MONTH values between 1 and the length of the month. A non-lenient GregorianCalendar throws an exception upon calculating its time or calendar field values if any out-of-range field value has been set.