isset() is generally useful in PHP because it's a loosely-typed language
that doesn't require variable declarations. In Java, you can avoid a lot of
these issues because the compiler picks up situations where you try to use a
variable without declaring it beforehand, or if it's likely to have been
unassigned a value. For example:
String s;
if (some-conditional-test) s = "hello";
System.out.println(s);
...should be picked up by the compiler.
In a lot of other cases, you can often avoid returning null by returning
empty arrays or collections in Java. In many others, you can also carefully
arrange expressions, such as:
if ("something".equals(request.getParameter("abc"))) ...;
This is good practice in any case, as even if there's no such parameter
"abc", you'll always avoid a NullPointerException.
Hint (OT): with PHP, or other loosely-typed languages such as JavaScript,
try forcing types correctly by using literals before variables in
expressions. Instead of:
if (x > 0) ...
Write:
if (0 < x)
Back on topic, in all other cases, what's wrong with using try...catch to
handle NullPointerExceptions ? It's arguably much cleaner than mixing in
"if (isset($x))" throughout your code. You can arrange the normal flow of
execution, assuming everything goes well, within a try...catch block. If
exceptionnally something is null, handle this elsewhere. And if that
doesn't suit, just try:
if (null == mavariable) ...;
Hope this helps!
-Christopher Brown
----- Original Message -----
From: "Daniel Lynn" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Thursday, March 15, 2001 6:23 AM
Subject: isset()
> ok, in PHP there is a command called isset(). It returns a boolean to
> tell you if a certain variable was passed to the program or not. (Helps
> eliminate those nullpointer exceptions without putting everything in
> try/catch statements) Now, I was looking for one in JSP and I'm having a
> little trouble. I think it may just be I don't know what I'm looking
> for, so if anyone would be so kind as to let me know the name of the
> function if it exists it'd be MUCH appreciated. Thank you in advance.
>
> -Daniel
>
>
===========================================================================
> To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff
JSP-INTEREST".
> For digest: mailto [EMAIL PROTECTED] with body: "set JSP-INTEREST
DIGEST".
> Some relevant FAQs on JSP/Servlets can be found at:
>
> http://java.sun.com/products/jsp/faq.html
> http://www.esperanto.org.nz/jsp/jspfaq.html
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
> http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
===========================================================================
To unsubscribe: mailto [EMAIL PROTECTED] with body: "signoff JSP-INTEREST".
For digest: mailto [EMAIL PROTECTED] with body: "set JSP-INTEREST DIGEST".
Some relevant FAQs on JSP/Servlets can be found at:
http://java.sun.com/products/jsp/faq.html
http://www.esperanto.org.nz/jsp/jspfaq.html
http://www.jguru.com/jguru/faq/faqpage.jsp?name=JSP
http://www.jguru.com/jguru/faq/faqpage.jsp?name=Servlets
