Exception Handling

[sunil langeh]

Hi Rancher's, Can anybody list "Checked & Unchecked Exceptions" as it creates lot of confusions to analyze ...

[Freddy Wong]

I believe there are a lot of similar threads like this here. Have you tried to search it? And don't forget, Google is your best friend

[sunil langeh]

Thanks Freddy for quick reply, ya i tried many of the same threads but still failure to found out the exact,,,,,

[Vinayak Bhat]

Better Still. check the API
http://java.sun.com/j2se/1.5.0/docs/api/

All Subtypes of class Exception are checked exceptions except for RuntimeException and its subclasses.
RuntimeException are unchecked exception and so are its subclasses.

-VB

[Freddy Wong]

In summary,
checked -> you need to catch or re-throw it. If you re-throw it, you need to declare the exception. It extends from Exception
unchecked -> you don't need to catch it. If you re-throw it, you don't need to declare the exception. It extends from RuntimeException

Hope this helps.

[sunil langeh]

Thanks Freddy & Vinayak, I have one more doubt, Why is it so that checked exceptions must be handled or declared and not RuntimeException(and its subclasses) while both are inherited from Exception. If something like this:

 
Exception ex = new CheckedException(); //possible right
Exception ex = new RuntimeException(); // also possible
   

[Freddy Wong]

Why is it so that checked exceptions must be handled or declared and not RuntimeException

Because it's defined in the Java Language Specification

[Jesper de Jong]

Some background information:

The people who invented the Java language thought it was a good idea to have to kinds of exceptions: checked and unchecked exceptions. The idea was probably that checked exceptions should be used for normal, "expected" error conditions, and unchecked exceptions should be used for unexpected error conditions in a program (for example errors that would indicate that's there a bug in the program).

Other programming languages have exceptions too, but Java is unique in that it has two kinds of exceptions.

There has been some debate on the Internet on whether it was a good idea to have these two kinds of exceptions. There are some people who think that checked exceptions are not useful and should not have been put into the language.

[Vinayak Bhat]

sunil langeh wrote:Thanks Freddy & Vinayak, I have one more doubt, Why is it so that checked exceptions must be handled or declared and not RuntimeException(and its subclasses) while both are inherited from Exception. If something like this:

 
Exception ex = new CheckedException(); //possible right
Exception ex = new RuntimeException(); // also possible
   

Sunil, Checked Exception are compile time errors, if you don't handle them the compiler won't compile the code and you won't get the class file. So you are not getting any further. Runtime exception, the compiler doesn't bother to check. You can go through the KS && BB SCJP book. I am sure lots of your questions will be answered in the book.
Cheers
Vinayak

[Jesper de Jong]

Vinayak Bhat wrote:Sunil, Checked Exception are compile time errors, if ...

It's a bit confusing to say "checked exceptions are compile time errors" - an exception is not a compile-time error.

Checked exceptions are called 'checked' because the compiler checks if you properly handle them in your code (by catching them or declaring with a 'throws' declaration that your method throws them to the calling method).

For unchecked exceptions, the compiler does not require you to handle the exception.