Comparing date strings in Java

So I am using dateString1.compareTo(dateString2) which does a lexicographic comparison with strings, based on the Unicode value of each character, and returns an int. Here is a code sample.

String dateString1 = "05-12-2012";
String dateString2 = "05-13-2012";
if (dateString1.compareTo(dateString2) <=0){
   System.out.println("dateString1 is an earlier date than dateString2");
}

Is this a wrong approach to compare dates in Java?

In my tests, I have not run into a situation where I have gotten unexpected result. I really do not want to create a Date object out of the string, if I don't have to, because I am doing this inside a long running loop.

Ninja Edit Gleaning from the answers below there is nothing wrong with comparing dates as a string if it is in yyyyMMdd format but if it is in any other format it will obviously result in error.

I actually have my date string as yyyyMMdd format in my actual code. (I typed the format wrong in the example I gave above.) So for now, I will just leave the code as it is, and add few lines of comments to justify my decision.

But I now see that comparing strings like this is very limiting and I will run into bugs if dba decides to change the date format down the road, which I don't see happening.

java date

Edit Report

Use strings to handle dates in Java is not always the best option. For example, when it is a leap year, February has an extra day. Because strings can be seemingly correct, it is more appropriate to perform a conversion. Java validates that the date is correct.

You can convert strings to dates using the SimpleDateFormat class.

public static void main(String[] args) throws ParseException {
    String dateString1 = "05-12-2012";
    String dateString2 = "05-13-2012";

    SimpleDateFormat format = new SimpleDateFormat("dd-MM-yyyy");

    Date date1 = format.parse(dateString1);
    Date date2 = format.parse(dateString2);

    if (date1.compareTo(date2) <= 0) {
        System.out.println("dateString1 is an earlier date than dateString2");
    }
}

To find out which parameters are allowed to check Customizing Formats (The Java™ Tutorials > Internationalization > Formatting)

answered 2012-05-15T22:34:34.553

Comparing date strings in Java

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