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Date format conversion

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wwworg

wwworg

Programmer
Feb 10, 2006
35
CA
Hey guys

I am using tomcat 5.5, J2SE 1.5 with Oracle 8i

Here is a function I have that converts a date like (18-06-2006) to (18-JUN-2006).

<%! public String changeDateFormat(String str) throws java.text.ParseException {
SimpleDateFormat df = new SimpleDateFormat("dd-MM-yyyy");
java.util.Date tDate = new java.util.Date();
tDate = df.parse(str);
df = new SimpleDateFormat("dd-MMM-yyyy");
String date1 = df.format(tDate).toUpperCase();
return date1;
}
%>

What I want to be able to do is convert a date like (9999-12-30) to (30-DEC-9999). What Modifications do I need to make to this function to be able to do this. Because curently if I pass (9999-12-30) as a parameter, it gives an error saying "unparseable date".

Any help would be highly appreciated.

Thanks
 
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You just have to switch the way that the SimpleDateFormat is constructed.

Instead of using "dd-MM-yyyy", you would use "yyyy-MM-dd" :
Code: 
<%! 
public String changeDateFormat(String str) throws java.text.ParseException {
    SimpleDateFormat df = new SimpleDateFormat("[b]yyyy-MM-dd[/b]");
    java.util.Date tDate = new java.util.Date();
    tDate = df.parse(str);
    df = new SimpleDateFormat("dd-MMM-yyyy");
    String date1 = df.format(tDate).toUpperCase();
    return date1;
   }     
%>

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Yes, I understand that, but there will also be some dates in (dd-mm-yyyy) format that I also want to convert to (dd-MON-yyyy). So I believe I need to a way to find out the format of incoming data parameter. So if incoming date is (yy-mm-dddd) then do SimpleDateFormat df = new SimpleDateFormat("dd-mm-yyyy");

and if incoming date is yyyy-mm-dd then do SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");

I am just not sure how to find that format?? or there is any other way to do.

Thanks for your response sedj. I will appreciate a little help here.

Thanks
 
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Well you will have to work out that bit yourself, probably using regular expressions or something like that. Without actually knowing the rules to which your dates conform, I cannot really help you any further !

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Please don't do that - it is a really filthy horrible way of using exception blocks - really, really bad idea IMO.

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Hey guys

I have tried to do this

if (str.indexOf("-") == 5)
{
SimpleDateFormat df = new SimpleDateFormat("yyyy-M-dd");
java.util.Date tDate = new java.util.Date();
tDate = df.parse(str);
df = new SimpleDateFormat("dd-MMM-yyyy");
String date1 = df.format(tDate).toUpperCase();
return date1;
}
else
{
SimpleDateFormat df = new SimpleDateFormat("dd-M-yyyy");
java.util.Date tDate = new java.util.Date();
tDate = df.parse(str);
df = new SimpleDateFormat("dd-MMM-yyyy");
String date1 = df.format(tDate).toUpperCase();
return date1;
}

but I am still getting that error "unparseable date". Is there something wrong with this above code??

Thanks guys
 
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You can also use the parse method of SimpleDateFormat class. It will return a null value if the format is not the speicifed.

Cheers,
Dian
 
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I don't think it will Dian - it'll throw an exception.

If you defintely have only two date formats :

dd-MM-yyyy and yyyy-MM-dd , then I would say this would be fine :

Code: 
String date = "2006-02-28";
SimpleDateFormat df = null;if (date != null) {
  String dateParts = date.split("-");
  if (dateParts.length > 1) {
    int firstPartLen = dateParts[0].length();
    if (firstPartLen  == 4) {
       df = new SimpleDateFormat("yyyy-MM-dd");
    } else if(firstPartLen == 2) {
       df = new SimpleDateFormat("dd-MM-yyyy");
    } else {
       df = null;
    }
  }


  if (df == null) {
    // error now - format not recognized !
  } else {
        java.util.Date tDate = new java.util.Date();
        tDate = df.parse(str);
        df = new SimpleDateFormat("dd-MMM-yyyy");
        String date1 = df.format(tDate).toUpperCase();
        return date1;
  }

  return null;
}

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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formatting gone funny above :

Code: 
String date = "2006-02-28";


SimpleDateFormat df = null;

if (date != null) {
  String dateParts = date.split("-");
  if (dateParts.length > 1) {
    int firstPartLen = dateParts[0].length();
    if (firstPartLen  == 4) {
       df = new SimpleDateFormat("yyyy-MM-dd");
    } else if(firstPartLen == 2) {
       df = new SimpleDateFormat("dd-MM-yyyy");
    } else {
       df = null;
    }
  }
}


if (df == null) {
	// error now - format not recognized !
} else {
	java.util.Date tDate = df.parse(str);
	df = new SimpleDateFormat("dd-MMM-yyyy");
	String date1 = df.format(tDate).toUpperCase();
	return date1;
}

  return null;
}

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Yeah I know Dian - but using exceptions in that way is horrible and messy and just bad practice - think of the stack you'll be creating ! Much better and quicker to handle it programmatically.

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Ah Ha !
Quoted from "Core java - Volume 1 - Fundamentals", page 576, published by Sun itself

There is a tendency to overuse exceptions ... exception handling is not supposed to replace a simple test.
The book then goes on to describe, and demonstrate how it is slower to use exceptions than to do a simple test.

--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
Click to expand...
Click to expand...
 
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I know, so he can use this other method to check wether the format is the correct one and act in consequence.

Cheers,
Dian
 
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But that does not seem to return null for an incorrect format (as defined as incorrect by OP).

Eg :

Code: 
String date = "01-02-2006";
SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd");
java.util.Date d = df.parse(date, new ParsePosition(0));
System.out.println(d);

Rather than "null", I get "Fri Jul 30 00:00:00 GMT 0006" ...


--------------------------------------------------
Free Java/J2EE Database Connection Pooling Software
 
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Hey guys, thanks for an interesting discussion
I used to code submitted by sedj but it is now setting df to null. This very strange

here is the code

<%! public String changeDateFormat(String str) throws java.text.ParseException {
SimpleDateFormat df = null;
if (str != null) {
String [] dateParts = str.split("-");
if (dateParts.length > 1) {
int firstPartLen = dateParts[0].length();
if (firstPartLen == 4) {
df = new SimpleDateFormat("yyyy-MM-dd");
} else if(firstPartLen == 2) {
df = new SimpleDateFormat("dd-M-yyyy");
} else {
df = null;
}
}
}
if (df == null) {
//error now - format not recognized !
return "21-JUL-2008";
} else {
java.util.Date tDate = df.parse(str);
df = new SimpleDateFormat("dd-MMM-yyyy");
String date1 = df.format(tDate).toUpperCase();
return date1;
}
}
%>

Also, can please someone tell me how to put the code inside the code editor here. using <code<</code>????

Thanks guys.
 
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