How to Validate Date Against multiple patterns format in Java?

问题

My problem is not "how to do it", my problem is the corner cases involved. Here is my code and test case.

package datetest.com;

import java.text.ParseException;
import java.text.SimpleDateFormat;

public class MultipleDateParserFormat {
    private final static String[] PossibleDateFormat=new String[]{
        "MM/dd/yyyy",
        "MM.dd.yyyy",
        "MM-dd-yyyy",
        "yyyy/MM/dd",
        "yyyy.MM.dd",
        "yyyy-MM-dd",
        "dd/MM/yyyy",
        "dd.MM.yyyy",
        "dd-MM-yyyy"
        };

    public MultipleDateParserFormat(){};
    public void checkParseDate(String passedDate){
        int PossibleDateFormatLength=PossibleDateFormat.length;

        for(int i=0;i<PossibleDateFormatLength;i++){
            try {
                SimpleDateFormat simpleDateFormant=new SimpleDateFormat(PossibleDateFormat[i]);
                simpleDateFormant.setLenient(false);
                java.util.Date date= simpleDateFormant.parse(passedDate);
                System.out.println(date);

            } catch (ParseException e) {

                System.out.println("Parse Exception Occured for your input Value"+passedDate + "for format" + PossibleDateFormat[i]);
            }
        }


    }

    public static void main(String...strings){

        String passedDate="4-03-1992";// This test case is validating against two Pattern 

        MultipleDateParserFormat multipleDateParserFormat= new MultipleDateParserFormat();
        multipleDateParserFormat.checkParseDate(passedDate);
    }

}

Here is the OUTPUT that I am getting when I run this code:

Parse Exception Occured for your input Value4-03-1992for formatMM/dd/yyyy
Parse Exception Occured for your input Value4-03-1992for formatMM.dd.yyyy
Fri Apr 03 00:00:00 IST 1992
Parse Exception Occured for your input Value4-03-1992for formatyyyy/MM/dd
Parse Exception Occured for your input Value4-03-1992for formatyyyy.MM.dd
Parse Exception Occured for your input Value4-03-1992for formatyyyy-MM-dd
Parse Exception Occured for your input Value4-03-1992for formatdd/MM/yyyy
Parse Exception Occured for your input Value4-03-1992for formatdd.MM.yyyy
Wed Mar 04 00:00:00 IST 1992

Since my test case is satisfying two given patterns, I'm getting two outputs.

How can I avoid such cases here? What are other ways to do such multiple pattern validation?

回答1:

I think the only reliable way is to know date format in advance. You can never know if 01/01/2014 is dd/MM/yyyy or MM/dd/yyyy

回答2:

Patterns MM-dd-yyyy and dd-MM-yyyy are both valid for 4-03-1992. That is why you get 2 results that pass. If you want to test to only allow one through then set one field to >12.

As for another way - there are many different ways. Personally I wouldn't want to rely on exceptions being thrown. Look in to the Regex API in Java:

http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

You can figure it out from there.

回答3:

Seems you need some sort of simple classifier:

Take big set of training texts.
Process them, counting and remembering frequencies for every pattern.

Then, if multiple matches are found, take one of pattern with greater frequency.

It won't give 100% accuracy, but will significantly improve it. It is important to take training data from sources close to that you will use and for the same language/region. For example, in Russia we never use mm/dd/yyyy nor mm.dd.yy, but for US it is a very common format.

来源：https://stackoverflow.com/questions/29751244/how-to-validate-date-against-multiple-patterns-format-in-java

标签

java

simpledateformat