Adding a specific date

Question

hi again, instead of prolonging(add) my current date to a month, how do i prolong a specific date? for an example my expiry date is in a week that is december 16th, how do i get a date that is a month from 16th.
thnks in advance

Answer 1

Heya -- gonna try to answer everything in one post =)
tried it. what i got is this error --
C:\servlet\ExpiryDate.java:11: invalid method
declaration; return type required
     public getDate() {
^
1 error
This was because you didn't specify what this method was returning. If you don't want it to return anything, make it void. Or perhaps you want it to return a Date object to be used in your main method.
import java.util.*;You don't need this import statement if you're specifying everything. That is, if you're using java.util.Date, you don't need to import java.util.*. If you do import java.util.*, then you'd only need to use Date in your code -- the compiler would assume you mean java.util.Date.
// Adding a month to the Calendar
objectdateToBeTested.add( java.util.Calendar.MONTH, 1 );
// Alternatively:
dateToBeTested.add( java.util.Calendar.DAY_OF_MONTH, 30 );Just to clarify: the "objectdateToBeTested" line (where'd the 'object' part come from? :) ) adds one month to the Calendar object. The "dateToBeTested" line adds 30 days to the Calendar object. I wasn't sure which one you wanted -- sometimes adding a month can be more or less than 30 days, so use only the one that makes sense for your application.
what if i do not want to specify the date. i mean hard coded the date. i want to get from some other source and set the date of the source to a month later.Right right. This is why I included the SimpleDateFormat object -- in the one I gave you, it's build to accept any String in the format: "MM-dd-yyyy". In the example I gave you, it used the String "12-16-2003". You can get this String anywhere, however. Let's say you're getting the string by calling a method getExpirationDate(), and let's assume that getExpirationDate() is returning a String in the format "MM-dd-yyyy". You could then use: "java.util.Date expirationDate = dateFormatter.parse( getExpirationDate() );" and expirationDate would then be initialized to the date returned by that method.
my actual question is do i need to throw an exception for using the dateFormatter to parse the date? met some error during compiling, asked me to throw or catch an exception.You do need to catch or throw an exception. The reason for this is what if you give the dateFormatter.parse( String dateStringToBeParsed ) method a String that isn't in the "MM-dd-yyyy" format? This would throw an exception, which means you need to let the program know how to handle that. Here's a working program:
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;
public class ExpiryDate {
    public static void main(String[] args) {
        System.out.println ( getExpirationDateString() );
        System.out.println ( getExpirationDatePlusOneMonth() );
    public static Date getExpirationDatePlusOneMonth() {
        SimpleDateFormat dateFormatter
             = new SimpleDateFormat( "MM-dd-yyyy");
        Date expirationDate = null;
        try {
            expirationDate = dateFormatter.parse(getExpirationDateString());
        } catch (ParseException e) {
            return null;
        Calendar dateToBeTested = Calendar.getInstance();
        // Initializing the Calendar object to the expiration
        dateToBeTested.setTime(expirationDate);
        // Adding a month to the Calendar
        dateToBeTested.add(Calendar.MONTH, 1);
        return dateToBeTested.getTime();
    public static String getExpirationDateString() {
        return "12-16-2003";
}Running this will give:
12-16-2003
Fri Jan 16 00:00:00 EST 2004
(The second line is formatted differently because it's printing out a Date object instead of a String object -- Date objects are displayed that way by default when printed. You can use the SimpleDateFormatter object to format the Date object into the "MM-dd-yyyy" format, but I'll leave that for later.)
Notice that the ParseException was caught -- the ParseException gets thrown if the String supplied to the parse method is invalid. In that case, the method returns null -- which seems valid to me: if you can't parse the String, it makes sense that the method should return nothing. That's the key to catching exceptions: handling possible errors gracefully.
Sorry -- this was a lot of info. Let me know if you need anything elaborated on =)
Jim
P.S. I made those methods static so you wouldn't have to create an object to call them. In this case, static means class-wide -- that is, those two methods, just like the main method, are not attached to one specific instance of the class. Hope that doesn't confuse everything.