Convert String to a Number

[wgcs]

I have browsed the "Java Language Specification" at

http://java.sun.com/docs/books/jls/second_edition/html/jTOC.doc.html

and the String class reference

http://java.sun.com/j2se/1.4/docs/api/java/lang/String.html

but I can't find the "right" way to convert a string that represents a number in Ascii into a number that can be used in computations.

How do I do it?

 

[Targol]

What you can do :

String toto= new String("1234");
Integer totoInt = new Integer(toto);
int totoVal = totoInt.intValue();

hope that helps. Water is not bad as soon as it stays out human body ;-)

 

[wgcs]

It helped alot, Thanks! I had just found the Integer( String ) constructor, but the examples helped me put it all together. Can you tell me if this is good Java code (It does compile, but it seems a little long-winded) for validating a CC expiration date against today's date?

 Calendar cal = new GregorianCalendar();
 int year  = new Integer( cal.get(Calendar.YEAR)    ).intValue(); // 2002
 int month = new Integer( cal.get(Calendar.MONTH)+1 ).intValue(); // 0=Jan, 1=Feb, ...
 month++; // Correct for 0-based calendar
     
 // // Parse decimal string
 int nowYr = new Integer(req.getParameter("PayExpMo")).intValue();
 int nowMo = new Integer(req.getParameter("PayExpYr")).intValue();

 if (  (nowYr>year) || ( (nowYr==year) && (nowMo>month) ) )
  { errorlist += "The Credit Card has already Expired."; }

 

[Targol]

I think a better way to do it is to use one of these methods from the Date Object :
after, before or compareTo

See

http://java.sun.com/j2se/1.3/docs/api/java/util/Date.html

for more details. Water is not bad as soon as it stays out human body ;-)

 

[xutopia]

I think if you have two dates you can simply do

if (date1 < date2) Gary

http://www.xutopia.com

Haran

 

[toolkit]

Here is some sample code to play with :

import java.util.Date;
import java.util.Calendar;
import java.text.DateFormat;
import java.text.SimpleDateFormat;

public class CCExpire {

  private static final DateFormat df = new SimpleDateFormat("dd MMM yyyy HH:mm:ss:SSS");

  private Calendar expiry = Calendar.getInstance();

  public CCExpire(String month, String year) 
      throws IllegalArgumentException, NumberFormatException
  {
    if(year.length() != 4)
      throw new IllegalArgumentException("year must be 4 digits");
    /*
       The card is valid up to and including the last day of the expiry
       month, so set the expiry date as the first day of the next month.
       Remember that months are 0-based so:

       m = Integer.parseInt(month) - 1   // to make 0-based
                                   + 1   // to make next month
    */
    int m = Integer.parseInt(month);
    int y = Integer.parseInt(year);
    expiry.set(Calendar.MONTH, m);
    expiry.set(Calendar.YEAR, y);
    expiry.set(Calendar.DATE, 1);
    expiry.set(Calendar.HOUR_OF_DAY, 0);
    expiry.set(Calendar.MINUTE, 0);
    expiry.set(Calendar.SECOND, 0);
    expiry.set(Calendar.MILLISECOND, 0);

    synchronized(df) {
      System.out.println("Expires: "+df.format(expiry.getTime()));
    }
  }

  public boolean isExpired() {
    return new Date().after(expiry.getTime());
  }

  public static void main(String[] args) {

    CCExpire ccard = null;

    if(args.length != 2)
      System.exit(0);

    try {
      ccard = new CCExpire(args[0], args[1]);
      synchronized(df) {
        System.out.println(df.format(new Date())+" expired: "+ccard.isExpired());
      }
    } catch(Exception e) {
      e.printStackTrace();
    }
  }
}

HTH, Cheers Neil ;-)

 

[wgcs]

Thanks, Neil;

That looks like the reusable, truly-Java way to do it!