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string and object (null considered string?)

Margaret Tan
Greenhorn

Joined: Sep 14, 2001
Posts: 20
Hi guys,
I have 2 questions regarding the following code. First question, why is it that null here is considered as a string and it would run if I will not include the object created with whatever. Second question, why do I get an error msg when I include whatever that it cannot resolve symbol?

[This message has been edited by Cindy Glass (edited October 25, 2001).]
Michael Bruesch
Ranch Hand

Joined: Sep 23, 2001
Posts: 158
ok, I'm not sure what you're asking here Mag...I compiled the code, but put quotation marks around "whatever" to make it a String. The output was: String String. But I'm still not sure what you're asking??
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Michael J Bruesch
Codito, ergo sum...
I code, therefore I am.
[url = http://www.geocities.com/mjbruesch/games]My Java Games, I'm quite proud[/url]


Michael J Bruesch<br /><i>I code, therefore I am.</i>
Jane Griscti
Ranch Hand

Joined: Aug 30, 2000
Posts: 3141
Hi Margaret,
'null' is really a 'null literal'. It's valid in Java and can be legally assigned to an Object; which is why <code>new Sample(null)</code> works. It gets treated as a String vs an Object because, when given a choice between two methods where the argument is valid for both parameters, the compiler will always choose the most specific parameter as a match. In this case, 'null' is a literal that can be handled as an Object and a String. String is more specific so the compiler uses <code>Sample(String s)</code> vs <code>Sample(Object o)</code>
'whatever' has no meaning in Java; it's not a literal or a built-in object and you haven't given it any definition so the compiler doesn't know what it is and gives you an error.
Hope that helps.
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Jane Griscti
Sun Certified Programmer for the Java� 2 Platform


Jane Griscti
SCJP, Co-author Mike Meyers' Java 2 Certification Passport
Margaret Tan
Greenhorn

Joined: Sep 14, 2001
Posts: 20
Jane,
I still do not fully grasp why Java does this but it is a bit clearer now, thanks!
 
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