RE: field initializtion

I guess my main question is so I don't have to check for null.  Because..

if ((field !=null) && (!field.equals("text"))

will work fine if field is null.  But...

if ((field == null) || (field.equals("text"))

will fail if field is null with a null pointer exception error.  So, to
check for null or "" (basically a blank value) a little extra work is
involved.

I know it's safer to check for not equals, but sometimes it's nicer to not
do that.  Inevitably there will be a point where I will forget to check for
null and my program will bomb at runtime with a null pointer exception.
That's really what I want to avoid.  But there's no *PSSR in Java.  ;)

Brad

> -----Original Message-----
> From: Joe Pluta [mailto:joepluta@plutabrothers.com]
> Sent: Monday, March 26, 2001 11:58 AM
> To: JAVA400-L@midrange.com
> Subject: Re: field initializtion
> 
> 
> What is "correct" depends on the usage.  In some cases, a 
> zero-length string may be a valid return, with a null 
> indicating an error.  For example, extra parameters for an 
> HTML tag would return "" if the tag was set to have no extra 
> parameters, but null if the tag has never been set up at all.
> 
> That particular case aside, Java methods returning String 
> will commonly return null - this indicates that whatever 
> method is used to initialize the field was never invoked.
> 
> As to initialization, instance variables of type String (or 
> indeed of any non-primitive type) are initialized to null.  
> Temporary variables are not initialized, and if the compiler 
> recognizes that you are attemping to use a field without 
> intializing it, it will generate a compile-time error.
> 
> Finally, there is a little-discussed feature of the compiler 
> that says that when you assign a literal value to two 
> different String objects, they may actually get the exact 
> same address - this helps reduce heap space requirements.  It 
> also allows two String literals to be compared using the == 
> and != operators, although I tend to avoid this particular 
> bit of "clever" coding.
> 
> Joe
> 
> 
> ---------- Original Message ----------------------------------
> From: "Stone, Brad V (TC)" <bvstone@taylorcorp.com>
> Reply-To: JAVA400-L@midrange.com
> Date: Mon, 26 Mar 2001 11:32:24 -0600
> 
> >What is more correct and why when creating local work fields 
> in a method?
> 
> String newString = new String();
> or
> String newString = null;
> or
> String newString = "";
> 
> How about when you're creating a class?  I've read that a 
> class that returns
> a null attribute is a pain in the arse.  So, would you simple use the
> constructor to change the value from null to ""?  for example
> 
> Class MyClass {
>   String value = null;
> 
>   public MyClass() {
>     value="";
>   }
> }
> 
> +---
> | This is the JAVA/400 Mailing List!
> | To submit a new message, send your mail to JAVA400-L@midrange.com.
> | To subscribe to this list send email to JAVA400-L-SUB@midrange.com.
> | To unsubscribe from this list send email to 
> JAVA400-L-UNSUB@midrange.com.
> | Questions should be directed to the list owner: joe@zappie.net
> +---
> 
> +---
> | This is the JAVA/400 Mailing List!
> | To submit a new message, send your mail to JAVA400-L@midrange.com.
> | To subscribe to this list send email to JAVA400-L-SUB@midrange.com.
> | To unsubscribe from this list send email to 
> JAVA400-L-UNSUB@midrange.com.
> | Questions should be directed to the list owner: joe@zappie.net
> +---
> 
+---
| This is the JAVA/400 Mailing List!
| To submit a new message, send your mail to JAVA400-L@midrange.com.
| To subscribe to this list send email to JAVA400-L-SUB@midrange.com.
| To unsubscribe from this list send email to JAVA400-L-UNSUB@midrange.com.
| Questions should be directed to the list owner: joe@zappie.net
+---