showInputDialog

Thread view:

Eitan M - 04 Apr 2006 08:36 GMT

Hello,
I have use in my program :
s = JOptionPane.showInputDialog( ....)

when I press just OK,
s should be "",
but if I ask in my program :
if (s=="") ...
the result of if statment is false.

Also I cannot catch case when the user press "Cancel",

So What I did is :
if (s == null || s.length() = 0)
instead of
if (s == 0)

why (s==0) doesn't work properly ?
And what should I do in my code ?

Thanks :)

Reply to this Message

Thomas Weidenfeller - 04 Apr 2006 10:01 GMT

> when I press just OK,
> s should be "",
> but if I ask in my program :
> if (s=="") ...
> the result of if statment is false.

You want to dig out a Java text book and learn about how to do proper
string comparison in Java. You are not comparing string contents in your
code, you are just comparing string references. You would have to be
lucky if these two references indeed point to the same string.

> why (s==0) doesn't work properly ?

Again, get out a text book about Java. This is basic Java syntax. A
string is not an integer, and there is no such thing as an implicit type
conversion between String and int. If you want such stuff, try C or C++.
There you can compare some integer value with a pointers to some memory
area which might or might not hold a string.

/Thomas

Signature

The comp.lang.java.gui FAQ:
ftp://ftp.cs.uu.nl/pub/NEWS.ANSWERS/computer-lang/java/gui/faq
http://www.uni-giessen.de/faq/archiv/computer-lang.java.gui.faq/

Reply to this Message

Eitan M - 04 Apr 2006 12:36 GMT

Sorry,
for my question, I have ment :

> why (s=="") doesn't work properly ?

instead of

> why (s==0) doesn't work properly ?

(s=="") returns false, even I just press OK button.

Why ?

Reply to this Message

Gregor Kovač - 04 Apr 2006 12:45 GMT

> Sorry,
> for my question, I have ment :
[quoted text clipped - 6 lines]
>
> Why ?

Maybe because == compares refereces and not values ?
Do (s.compareTo("") == 0)

Signature

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

| Gregor Kovac | Gregor.Kovac@mikropis.si |

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

| In A World Without Fences Who Needs Gates? |
| Experience Linux. |

-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~-~

Reply to this Message

Luc The Perverse - 04 Apr 2006 12:48 GMT

> Sorry,
> for my question, I have ment :
[quoted text clipped - 6 lines]
>
> Why ?

I'm not sure you listened to Thomas.

But s is an object (I'm presuming of type String) and "" is an object. The
== operator will only tell you if they are the same object.

Try ("".equals(s))

--
LTP

Reply to this Message

Roedy Green - 04 Apr 2006 15:40 GMT

On Tue, 4 Apr 2006 10:24:21 +0200, "Eitan M"
<no_spam_please@nospam_please.com> wrote, quoted or indirectly quoted
someone who said :

>if (s=="") ...
>the result of if statment is false.
[quoted text clipped - 5 lines]
>instead of
>if (s == 0)

see http://mindprod.com/jgloss/gotchas.html#COMPARISON

Signature

Canadian Mind Products, Roedy Green.
http://mindprod.com Java custom programming, consulting and coaching.

Reply to this Message

showInputDialog

Free Magazines