如何使用String的split方法验证日期？

Question

How do I validate a date(i mean that the date should not be invalid) using split method of string class? Further details: Each month should have their respective days and February should have 29 days only when it is a leap year and date should not exceed the present date.

Answer 1

I can recomment to use validate(String value) method from Apache Commons DateValidator :

import org.apache.commons.validator.routines.DateValidator;
...

// Get the Date validator
DateValidator validator = DateValidator.getInstance();

// Validate/Convert the date
Date fooDate = validator.validate(fooString);
if (fooDate == null) {
    // error...not a valid date
    return;
}

validate() returns parsed Date if valid or null if invalid.

If you want only to get true/false, then there is another boolean method isValid() . For example:

DateValidator validator = DateValidator.getInstance();
if (validator.isValid(date)) {
    System.out.println(date + " is valid");
} else {
    System.out.println(date + " is invalid");
}

Answer 2

In the JDK, you have SimpleDateFormat to handle this kind of stuff.

For instance, to validate an hour:

final DateFormat fmt = new SimpleDateFormat("HH:mm");

Then you can try and parse:

fmt.parse(input);

It will throw a ParseException if the date is invalid.

Of course, many other formats can be done.

As to external libraries, if you have to/want to use one, there is really only one to consider: Joda Time . It is so good a library that Java 8's new date API is 90+% inspired by it.

NOTE: JDK's as well as Joda Time's, parsers will derive missing components in a date from the current time; it means that if you try and parse a string containing Feb 29 in 2015, it will fail... But it will succeed in 2016 since it is a leap year!

Answer 3

convert string to date format, and this is easy for validating 

public class DateUtil {

    // List of all date formats that we want to parse.
    // Add your own format here.
//u can use anyone format
    private static List<SimpleDateFormat>; 
            dateFormats = new ArrayList<SimpleDateFormat>() {{
            add(new SimpleDateFormat("M/dd/yyyy"));
            add(new SimpleDateFormat("dd.M.yyyy"));
            add(new SimpleDateFormat("dd.M.yyyy hh:mm:ss a"));
            add(new SimpleDateFormat("dd.MMM.yyyy"));
            add(new SimpleDateFormat("dd-MMM-yyyy"));
        }
    };

    /**
     * Convert String with various formats into java.util.Date
     * 
     * @param input
     *            Date as a string
     * @return java.util.Date object if input string is parsed 
     *          successfully else returns null
     */
    public static Date convertToDate(String input) {
        Date date = null;
        if(null == input) {
            return null;
        }
        for (SimpleDateFormat format : dateFormats) {
            try {
                format.setLenient(false);
                date = format.parse(input);
            } catch (ParseException e) {
                //Shhh.. try other formats
            }
            if (date != null) {
                break;
            }
        }

        return date;
    }
}