The Java program accepts the date in any format as input and prints the month,

The Java program accepts the date in any format as input and prints the month,

Is it possible

I tried the following, any other alternative ways / ideas?

import java.text.*;

import java.util.*;


public class PrintMonth3{


    public static void main(String args[])throws Exception{

    String patterns[]={"dd.MM.yyyy","dd.MM.yy","dd.MMM.yyyy","dd.MMM.yy","d.MM.yyyy"};

    String input="4.06.2011";

    for(int i=0;i<patterns.length;i++)
        doPrintMonth(patterns[i],input);

    System.out.println("\nNot a valid date format..");


    }



    public  static void doPrintMonth( String pattern,String input ) {


    try{
    SimpleDateFormat sdf=new SimpleDateFormat(pattern);

    Date output=sdf.parse(input);


    String mon[]={"Jan","Feb","Mar","Apr","May","Jun","Jul","Aug","Sep","Oct","Nov","Dec"};
    int m=output.getMonth();
    System.out.println("\n\t" + mon[m] );
    System.exit(0);
    }
    catch(Exception e){}    


    }


}

Solution

Within a reasonable range, yes This is a working example that accepts various formats

I assume this German / European format:

DD. MM. YYYY HH:MM:SS:MMMM

(this means that I can't match any date format for the arrival of the month)

This is the class:

public class VariableDateParser {

    private static final Pattern DATE_PATTERN = Pattern
    .compile("((?:(?:\\d+(?:[./]\\s*)?)+)?)\\s*((?:(?:\\d+[:]?)+)?)");

    public Date getDate(final String dateString) {
        final Calendar calendar = Calendar.getInstance();
        final Matcher matcher = DATE_PATTERN.matcher(dateString);
        if (matcher.matches()) {
            final String dateGroup = matcher.group(1).trim();
            if (!"".equals(dateGroup)) {
                final Iterator<Integer> fields = Arrays.asList(
                    Calendar.DATE,Calendar.MONTH,Calendar.YEAR).iterator();
                final String[] items = dateGroup.split("\\D+");
                for (final String item : items) {
                    if ("".equals(item))
                        break;
                    else if (fields.hasNext()) {
                        final Integer field = fields.next();
                        calendar.set(field,Integer.parseInt(item) -
                           // months are 0-based,grrrr!!!
                           (field.equals(Calendar.MONTH) ? 1 : 0));
                    } else {
                        throw new IllegalArgumentException(
                            "Bad date part: " + dateGroup);
                    }
                }
            }
            final String timeGroup = matcher.group(2).trim();
            if (!"".equals(timeGroup)) {
                final Iterator<Integer> fields = Arrays.asList(
                    Calendar.HOUR,Calendar.MINUTE,Calendar.SECOND,Calendar.MILLISECOND).iterator();
                final String[] items = timeGroup.split("\\D+");
                for (final String item : items) {
                    if ("".equals(item))
                        break;
                    else if (fields.hasNext()) {
                        final Integer field = fields.next();
                        calendar.set(field,Integer.parseInt(item));
                    } else {
                        throw new IllegalArgumentException(
                            "Bad time part: " + timeGroup);
                    }
                }
            }

        } else
            throw new IllegalArgumentException(
                "Bad date string: " + dateString);
        return calendar.getTime();
    }

}

Test code:

public static void main(final String[] args) {
    VariableDateParser parser = new VariableDateParser();
    DateFormat df = DateFormat.getDateTimeInstance(
        DateFormat.MEDIUM,DateFormat.LONG,Locale.GERMAN);
    System.out.println(df.format(parser.getDate("11")));
    System.out.println(df.format(parser.getDate("11. 10.")));
    System.out.println(df.format(parser.getDate("11. 10. 4")));
    System.out.println(df.format(parser.getDate("11. 10. 2004")));
    System.out.println(df.format(parser.getDate("11. 10. 2004 11")));
    System.out.println(df.format(parser.getDate("11. 10. 2004 11:35")));
    System.out.println(df.format(parser.getDate("11. 10. 2004 11:35:18")));
    System.out.println(df.format(parser.getDate("11. 10. 2004 11:35:18:123")));
    System.out.println(df.format(parser.getDate("11:35")));
    System.out.println(df.format(parser.getDate("11:35:18")));
    System.out.println(df.format(parser.getDate("11:35:18:123")));
}

Output:

11.05.2011 15:57:24 MESZ
11.10.2011 15:57:24 MESZ
11.10.0004 15:57:24 MEZ
11.10.2004 15:57:24 MESZ
11.10.2004 23:57:24 MESZ
11.10.2004 23:35:24 MESZ
11.10.2004 23:35:18 MESZ
11.10.2004 23:35:18 MESZ
01.05.2011 13:35:24 MESZ
01.05.2011 13:35:18 MESZ
01.05.2011 13:35:18 MESZ

be careful:

This is a quick proof of concept, not a serious attempt to write such a class This will match many invalid formats and ignore many valid formats