Date Parsing using SimpleDateFormat and parsePosition

Question

I am trying to parse a String to Date Object.Previously I used parse(String) definition but a date like 4/1/2004 2:00:00asasasas was getting correctly parsed which was wrong.So i used the ParsePosition signature parse(String,parsePosition) and checked if the index is not equal to the length then its an invalid Date.But above logic fails for a String as "4/1/2004 2:00:00 AM.Although it's a valid date but due to index and length logic it says invalid date when I try to parse it in "M/dd/YYYY" format. the parser parses the correct date part and does not take whole String into consideration. Any way to achieve it ? formatStr can be any format pattern.

Please advise.

public static void main(String[] args) {
        String formatStr="M/dd/YYYY";
    SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault());
        String str = "4/1/2004 2:00:00 AM";

        ParsePosition pp1 = new ParsePosition(0);

        Date retDate = sd.parse(str, pp1);
        if(retDate==null ||pp1.getIndex()!=str.length() ){
            System.out.println("I have a invalid Date");

        }

    }

" it says invalid date when I try to parse it in "M/dd/YYYY" format" - well of course it does, because that format doesn't include the time, whereas your string value does. You want yyyy rather than YYYY mind you... — Jon Skeet
– Jon Skeet, Commented May 15, 2015 at 12:06
Thanks for the reply.Current API implementation accepts the String Text and the Date format pattern(can be M/d/y h:m:s a or M/dd/YYYY) .It depends on user as to what date format he wants . Current API parses the string 4/1/2004 2:00:00 AM perfectly using M/dd/YYYY pattern.So I was looking for a way that is Backward compatible which means it passes for 4/1/2004 2:00:00 AM but fails for 4/1/2004 2:00:00 abcd using the pattern "M/dd/YYYY" .I know its kind of lame but any direction would be helpful — ankurlu
– ankurlu, Commented May 15, 2015 at 12:30

Juan Marcos Armella · Accepted Answer · 2015-05-15 13:16:47Z

1

Use:

public static void main(String[] args) {
        String formatStr="MM/dd/yyyy hh:mm:ss aa";
    SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault());
        String str = "04/01/2004 02:00:00 AM";

        ParsePosition pp1 = new ParsePosition(0);

        Date retDate = sd.parse(str, pp1);
        if(retDate==null ||pp1.getIndex()!=str.length() ){
            System.out.println("I have a invalid Date");

        }

    }

Correct the formatStr to include hour in am/pm and year in minus. Also use two digits for month and day.

If you want to parse with abcd instead of AM / PM you can use regular expression split.

public static void main(String[] args) {
    String formatStr="M/dd/yyyy h:m:s";

    SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault());
        String str = "04/01/2004 2:00:00 abcd";

        String[] strDate = str.split(" .[a-zA-Z]");

        ParsePosition pp1 = new ParsePosition(0);

        Date retDate = sd.parse(strDate[0], pp1);
        if(retDate==null ||pp1.getIndex()!=strDate[0].length() ){
            System.out.println("I have a invalid Date");

        }
        else
        {
           System.out.println("I have a valid Date");

        }

    }

See: http://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html

edited May 15, 2015 at 13:16

answered May 15, 2015 at 12:15

Juan Marcos Armella

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2 Comments

ankurlu Over a year ago

Thanks I know that the correct date format would be MM/dd/yyyy hh:mm:ss aa But my current implementation parses 04/01/2004 02:00:00 AM successfully using the M/dd/YYYY pattern. try String formatStr="M/dd/YYYY"; String str = "4/1/2004 2:00:00 AM"; SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault()); Date retDate = sd.parse(str)

Juan Marcos Armella Over a year ago

So, you want this work for : String str = "4/1/2004 2:00:00 abcd" ?

Shar1er80 · Accepted Answer · 2015-05-15 12:19:10Z

Two ways you can fix your problem.

Parse just the date out of the String and use your format

public static void main(String[] args) throws Exception {
    String formatStr = "MM/dd/yyyy";
    SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault());
    String str = "4/1/2004 2:00:00 AM";

    ParsePosition pp1 = new ParsePosition(0);

    String justDate = str.substring(0, str.indexOf(" "));
    Date retDate = sd.parse(justDate, pp1);
    if (retDate == null || pp1.getIndex() != justDate.length()) {
        System.out.println("I have a invalid Date");
    } else {
        System.out.println("I have a valid Date");
    }
}

Or use the correct format for the String you're testing

public static void main(String[] args) throws Exception {
    String formatStr = "MM/dd/yyyy hh:mm:ss aa";
    SimpleDateFormat sd = new SimpleDateFormat(formatStr, Locale.getDefault());
    String str = "4/1/2004 2:00:00 AM";

    ParsePosition pp1 = new ParsePosition(0);

    Date retDate = sd.parse(str, pp1);
    if (retDate == null || pp1.getIndex() != str.length()) {
        System.out.println("I have a invalid Date");
    } else {
        System.out.println("I have a valid Date");
    }
}

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