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Java

Posted by Thomas Nilsen
Thomas Nilsen
14,957 Points

Implementing a date validator

I'm fairly new to java, and is just building small programs to get the feel for the language. Any tips on how I can improve this code would be greatly appreciated, Craig Dennis 

import java.util.Set;
import java.util.HashSet;
import java.util.Arrays;
import java.util.regex.Matcher;
import java.util.regex.Pattern;


enum DateValidator {
    DDMMYYYY(0, 2, 4),
    MMDDYYYY(2, 0, 4),
    YYYYMMDD(6, 4, 0);

    private final int dayIndex;
    private final int monthIndex;
    private final int yearIndex;

    private DateValidator(int dayIndex, int monthIndex, int yearIndex) {
        this.dayIndex = dayIndex;
        this.monthIndex = monthIndex;
        this.yearIndex = yearIndex;
    }

    private int getDay(String date){ return Integer.parseInt(date.substring(dayIndex, dayIndex + 2)); }
    private int getMonth(String date){ return Integer.parseInt(date.substring(monthIndex, monthIndex + 2)); }
    private int getYear(String date){ return Integer.parseInt(date.substring(yearIndex, yearIndex + 4)); }

    private static boolean isLeapYear(int y) {
        return (y % 4 == 0) && ((y % 100 != 0) || (y % 400 == 0));  }

    private boolean isDateLegal(String date) {
        final int day = getDay(date);
        final int month = getMonth(date);
        final int year = getYear(date);
        boolean isValid = false;

        final Set<Integer> values = new HashSet<Integer>(Arrays.asList(1, 3, 5, 7, 8, 10, 12));
        final int daysInFebruary = (month == 2 && isLeapYear(year)) ? 29 : 28;

        if (day > 0) {
            if (values.contains(month)) { isValid = day <= 31; } 
            else if (month > 0 && month < 13 && month != 2) { isValid = day <= 30; }
            else if (month == 2) isValid = day <= daysInFebruary;
        }

        return isValid;
    }

    private static boolean isDateFormatValid(String date) {

        final String DATE_PATTERN = "(^" + "[0-9]{2}\\.[0-9]{2}\\.[1-2][0-9]{3}|" +
                                     "[0-9]{2}\\-[0-9]{2}\\-[1-2][0-9]{3}|" + 
                                     "[0-9]{2}\\/[0-9]{2}\\/[1-2][0-9]{3}|" +
                                     "[0-9]{2}\\s[0-9]{2}\\s[1-2][0-9]{3}|" +
                                     "[0-9]{2}[0-9]{2}[1-2][0-9]{3}|" +
                                     "[1-2][0-9]{3}\\.[0-9]{2}\\.[0-9]{2}|" +
                                     "[1-2][0-9]{3}\\-[0-9]{2}\\-[0-9]{2}|" +
                                     "[1-2][0-9]{3}\\/[0-9]{2}\\/[0-9]{2}" + 
                                     "[1-2][0-9]{3}\\s[0-9]{2}\\s[0-9]{2}" +
                                     "[1-2][0-9]{3}[0-9]{2}[0-9]{2}" +")$";

        Pattern pattern = Pattern.compile(DATE_PATTERN);
        Matcher matcher = pattern.matcher(date);

        return matcher.matches();
    } 

    public boolean validate(String date) {
        return this.isDateLegal(date.replaceAll("[\\.\\-\\/\\s]", "")) && isDateFormatValid(date);
    }
}

class Main {
    public static void main(String[] args) {
        System.out.print(DateValidator.DDMMYYYY.validate("02.10.1990") ? "Date is valid" : "Date is NOT valid");
    }
}