You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
General <strong>Java</strong> Questions I<br />
Q: Is it possible to use switch with range of values?<br />
Ex:<br />
switch (iBegins){<br />
case 2 to 10:<br />
}<br />
Answer:<br />
not exactly like this but:<br />
switch (iBegins){<br />
case 2:<br />
case 3:<br />
case 4:<br />
case 5:<br />
case 6:<br />
case 7:<br />
case 8:<br />
case 9:<br />
case 10:<br />
/* do stuff */<br />
break;<br />
case 11:<br />
/* other stuff */<br />
}<br />
Jan Schaumann <br />
Q: Is there a general reason why nullpointer exceptions occur?<br />
Answer: Of course there is. A NullPointerException happens when you have a<br />
reference, it's set to null (or is a class or instance variable and has never been<br />
initialized), and you try to perform some operation on the object it points to. Since it<br />
really doesn't point to an object, you can't do that.<br />
--<br />
Chris Smith<br />
Q: I am aware that the exceptions in the catch statements must be of the same<br />
type or a super type of the exception thrown in the try block.<br />
My question is this:<br />
Is there any significance in the ordering of the catch statements after a try block?<br />
Answer: It is required to design you catch statement sequences with most derived<br />
exception class type first and progressing to the highest superclass. Else, the code<br />
will not compile.<br />
For a obvious reason, if the a catch block for a given class precedes a catch block for<br />
a type that is derived from the first, the second catch block will never be executed.<br />
--<br />
D. Michael Nelson<br />
Q: I wrote a program that use a few RS232 ports. The operators are unskilled<br />
and often start multiple instances of the program. Will someone please be so kind<br />
and tell me how I can prevent them doing it?<br />
Answer 1: The first instance might write a file. Subsequent instances could check for<br />
the existence of that file, or else check it's contents.<br />
Another method could involve creating a server socket on a specific port. Subsequent<br />
file:///F|/350_t/350_tips/general_java-I.htm (27 of 31) [2002-02-27 21:18:18]