17 replies to this topic

[arunjib]

i want to write a class in jave which can validate any inputed date. i.e., is the inputed date valid or not... please help me

[eafkuor]

Please give us more info, i.e. the date format. Give us some examples of valid dates.

[arunjib]

i want to use date format as dd/mm/yyyy

now i entered a date as qw/12/200a and this is not a valid date

34/13/2a01 its not a valid date

01/01/1940 is a valid date
1/1/1940 is also a valid date.
hope i given examples to understand u my requred format.
just help me this code only in core java

eafkuor said:

Please give us more info, i.e. the date format. Give us some examples of valid dates.

[eafkuor]

First of all, check the string to see if there are 2 '/' characters.
After that, use their position to get the 3 substrings that are supposed to be the day, the month, and the year. Then, just use Integer.parseInt(String s) to see if they're actually numbers and if they're in the right range (non negative, less than 31, less than 12..). Of course to check wether 30 is a valid day, you first have to check the month (february has only 28 days for example).

[arunjib]

so far i could think like the following code. if i input a date as ....... "123/1/2001" that will show a valid date. please help more

import java.io.*;

public class date

{

public static void main(String args[]) throws IOException

{

InputStreamReader read=new InputStreamReader(System.in);

BufferedReader in=new BufferedReader(read);

String s;

int count=0;

char b;

System.out.print("Input date [dd/MM/yyyy] format only ");

s=in.readLine();

int x=s.length();

for(int y=0;y<x;y++)

{

b=(s.charAt(y));

if(b=='/')

count=count+1;

}

if(count==2)

System.out.println("Valid Date");

else

System.out.println("Invalid Date");

//int p=s.indexOf('/');

//int p2=s.indexOf('/');

//System.out.println(s+"\t"+x);

}

}

eafkuor said:

First of all, check the string to see if there are 2 '/' characters.
After that, use their position to get the 3 substrings that are supposed to be the day, the month, and the year. Then, just use Integer.parseInt(String s) to see if they're actually numbers and if they're in the right range (non negative, less than 31, less than 12..). Of course to check wether 30 is a valid day, you first have to check the month (february has only 28 days for example).

[wim DC]

public static void main(String[] args) {

        String date1 = "qw/12/200a";

        String date2 = "34/13/2a01";

        String date3 = "01/01/1940";

        String date4 = "1/1/1940";


        validateDate(date1);

        validateDate(date2);

        validateDate(date3);

        validateDate(date4);

    }


    public static void validateDate(String date) {

        SimpleDateFormat sdf = new SimpleDateFormat("d/M/yyyy");

        sdf.setLenient(false);

        ParsePosition pos = new ParsePosition(0);


        Date d = sdf.parse(date, pos);

        if (d == null) {

            System.out.println(date + " is no valid date.");

        } else {

            System.out.println(date + " is a valid date.");

        }


    }

Note: "dd/MM/yyyy" would not validate 1/1/1940, as 'dd' means it would have to be '01' instead of just '1'.
Ditto with M. (M is case sensitive, m=minute, M=month)

If you don't use the parseposition, but just sdf.parse(String), it will not return null as date, but instead throw a parseException which must be caught. I find this a cleaner solution, than using errorthrowing.

It's easier using java's dateformat thing, because it would also check if it's a possible day, like 31/02/2011 doesn't exist. so it will return invalid.

[eafkuor]

Wow... you know every. effing. class :D

[wim DC]

Yes ^^
I knew the SimpleDateFormat class existed, was hoping it had an isValid() method or so... then looked at the javadoc, and since parse with the parseposition doesn't throws errors that was good enough for me :)

[arunjib]

SimpleDateFormat sdf = new SimpleDateFormat("d/M/yyyy");

error msg : cannot find symbol - class SimpleDateFormat
what is the reason?

[wim DC]

Propably import issues
Put these on top of your file. Outisde the class body:

import java.text.ParsePosition;

import java.text.SimpleDateFormat;

import java.util.Date;


public class SomeClass(){

...

}

[arunjib]

with the help of wim DC's post i could generate the following code

import java.io.*;

import java.text.ParsePosition;

import java.text.SimpleDateFormat;

import java.util.Date;


public class date2{

public static void main(String[] args) throws IOException

{

//     String date1 = "qw/12/200a";

//     String date2 = "34/13/2a01";

//     String date3 = "01/01/1940";

//     String date4 = "1/1/1940";


InputStreamReader read=new InputStreamReader(System.in);

BufferedReader in=new BufferedReader(read);

String s;

System.out.print("Input date [dd/MM/yyyy] format only ");

s=in.readLine();

        validateDate(s);

//       validateDate(date1);

//       validateDate(date2);

//       validateDate(date3);

//       validateDate(date4);

    }


    public static void validateDate(String date) {

        SimpleDateFormat sdf = new SimpleDateFormat("d/M/yyyy");

        sdf.setLenient(false);

        ParsePosition pos = new ParsePosition(0);


        Date d = sdf.parse(date, pos);

        if (d == null) {

            System.out.println(date + " is no valid date.");

        } else {

            System.out.println(date + " is a valid date.");

        }

    }

    }

now i want to calculate number of days of a specific date... suppose the date is 3/1/2011 (i.e., 3rd January, 2011)... the calculated date is 3rd day of 2011. if the date is 3/2/2011 .. the calculated date is 31+3=34th day of 2011. please help me

[wim DC]

import java.util.Calendar;

...

...

Calendar cal = Calendar.getInstance();

cal.setTime(d);

System.out.println(cal.get(Calendar.DAY_OF_YEAR) + "th day of year.");

Often when working with Date you'll be better of with the Calendar class. Cause the Date class.. well it sucks :D
And Java knows it, a lot is depracated, but many methods like the parsing still return Date, Just to be backwards compatible