I have used so many times of the try--catch block in a java class. Now here are my questions:
1) Under what circumstancesshould the try{}catch{} block be used?
2) Under what circumstancesmust the try{}catch{} block be used?
3) What are the general rules (if any) for the catch Exception(any valid eception object will do)?
Thanks
Scott
Use it when you should, and when you must, you must!
Can you be more specific? One place where you must is in this situation:
void f() {
try {
g();
catch (IOException e) {
...
}
}
void g() throws IOException {...}
... since IOException is a checked exception that isn't propagated through f.
Of course, maybe a better solution would be to redo f to throws IOException
and have a higher method do the catching!
> 1) Under what circumstances should the try{}catch{} block be used?
When the compiler complains about uncaught exceptions (and you don't want to throw them on).
> 2) Under what circumstances must the try{}catch{} block be used?
When the compiler complains about uncaught exceptions (and you can't throw them on).
> 3) What are the general rules (if any) for the catch Exception(any valid eception object will do)?
You must catch an Exception... unless you catch it as a Throwable. Or you at least have to have a catch for each specific exception type that is declared throwable in the code within the try block, or a common superclass of multiple exceptions (such as Exception).
Thanks for the help.
Let me try to readdress the issue, see if I really understand it.
1) try{}catch(TestException e){} block MUST preceded by a throw; no throw no catch?
2) If a function does NOT explicitly throw any Exception, still in try--catch block, the catch will capture an Exception object;
such as:
public void test(){
try{}
catch(Exception e){}
--Correct?
3)If an exception class is defined with a Throwable object in a constructor:
public class TestException extends RMSException {
public TestException(Throwable exception) {
super(exception);
}
THEN in a class:
public class testSession implements Filter {
public void doFilter(
ServletRequest req,
ServletResponse resp,
FilterChain chain)
throws ServletException, IOException {
//I can actually use
try{}
} catch (TestException e) {
e.printStackTrace();
even if I did not throw the TestException?
Thanks
Scott
