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General <strong>Java</strong> Questions I<br />
Q: Why developers should not write programs that call 'sun' packages?<br />
Answer: <strong>Java</strong> Software supports into the future only classes in java.* packages, not<br />
sun.* packages. In general, API in sun.* is subject to change at any time without<br />
notice.<br />
A <strong>Java</strong> program that directly calls into sun.* packages is not guaranteed to work on<br />
all <strong>Java</strong>-compatible platforms. In fact, such a program is not guaranteed to work even<br />
in future versions on the same platform.<br />
For these reasons, there is no documentation available for the sun.* classes.<br />
Platform-independence is one of the great advantages of developing in the <strong>Java</strong><br />
programming language. Furthermore, Sun and our licensees of <strong>Java</strong> technology are<br />
committed to maintaining backward compatibility of the APIs for future versions of the<br />
<strong>Java</strong> platform. (Except for code that relies on serious bugs that we later fix.) This<br />
means that once your program is written, the class files will work in future releases.<br />
For more details, see the article Why Developers Should Not Write Programs That<br />
Call 'sun' Packages.<br />
http://java.sun.com/products/jdk/faq/faq-sun-packages.html<br />
Q: Can garbage collector remove my singleton?<br />
A usually singleton..<br />
public class Single{<br />
private static Single single;<br />
private Single {}<br />
public static Single getInstance(){<br />
if(single==null){<br />
single = new Single();<br />
}<br />
return single;<br />
}<br />
}<br />
Well,, seems good ?<br />
But classes are objects too...so do <strong>Java</strong> 2 v1.3 class garbagecollecting? Meaning my<br />
singleton could dissapear if i dont keep a refrence to it (or the class itself) somewhere<br />
?<br />
If classes is not garbagecollected, that's pretty stupid, I dont want classes taking up<br />
memory when i perhaps never will use it again....<br />
Answer: No. Classes can define objects. That is, only the dynamic part of the class<br />
defines objects. The static part exists only in one place in memory and can not be<br />
duplicated. You can call the getInstance() method from anywhere in your program.<br />
<strong>Java</strong> requires however that you tell where to find the method, in this case in the<br />
Single class.<br />
Therefore, you should use<br />
Single.getInstance()<br />
to get the instance. This is (though it looks much like it) not an execution of a method<br />
on an object, but just a method call without object. Single is only used to find out<br />
which getInstance() method should be used, and where it is.<br />
file:///F|/350_t/350_tips/general_java-I.htm (19 of 31) [2002-02-27 21:18:17]
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