4 Types of exception and the code to handle them

Dear all,
I would like to know wheter runtime exception, errors exception, unchecked exception and checked exception are classified as the 4 types of exception.
What are the java coding of them? please help.

There are two main families of exception in Java: checked and unchecked.
The base class for all exceptions is Throwable. Java provides Exception and Error that extend Throwable. RuntimeException (and many others) extend Exception.
RuntimeException and its descendants, and Error and its descendants, are called unchecked exceptions. Everything else is a checked exception.
If your method, or any method it calls, can throw a checked exception, then your method must either catch that exception, or declare that your method throws that exception. This way, when I call your method, I know at compile time what can possibly go wrong and I can decide whether to handle it or just bubble it up to my caller. Catching a given exception also catches all that exception's descendants. Declaring that you throw a given exception means that you might throw that exception or any of its descendants.
Unchecked exceptions (RuntimeException, Error, and their descendants) are not subject to those restrictions. Any method can throw any unchecked exception at any time without declaring it. This is because unchecked exceptions are either the sign of a coding error (RuntimeException), which is totally preventable and should be fixed rather than handled by the code that encounters it, or a problem in the VM, which in general can not be predicted or handled.
http://java.sun.com/docs/books/tutorial/essential/exceptions/index.html

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Besides throwing exceptions and the "return;" statement

Besides throwing exceptions and the "*return*" statement, what else clauses could complete a code block abruptly?
Originally I thought System.exit() should be one of that kind, and I was totally puzzled by the fact that finally clause dose not work with System.exit(). But after a few thoughts, it becomes clear to me that System.exit() dose not even complete a code block, let alone completing a code block abruptly. So is there other logic that could make a code block complete abruptly?
My question originates from paragraphs in <Thinking in JAVA>, which claim that, I quote,
"Unfortuantely, there's a flaw in Java's exception implementation. Although exceptions are an indication of a crisis in your program and should never be ignored, it's possible for an exception to simply be lost. This happens with a particular configuration using a finally clause"..."This is a rather serious pitfall, since it means that an exception can be completely lost, and in a far more subtle and difficult -to-detect fashion..."..."Perhaps a future version of Java will repair this problem"...
After check with JLS, it seams that it is legitimate to ignore the reason for the abrupt completion of the try block, if the corresponding finally block completes abruptly. I think whether this is a "pitfall, flaw" or not depends on how deeply we language users understand the purpose of the finally clause and it is better for me to know all the possible reasons for a code block to complete abruptly.
So, besides throwing exceptions and the "*return*" statement, what else clauses could complete a code block abruptly?

warnerja wrote:
Case 1: Normal flow (no exception is about to be bubbled to the caller before getting to the finally block) - I'd say we want an exception back due to the failure to close the stream.
Case 2: The finally block was entered through an exception about to be bubbled to the caller - the caller can only get one or the other exception back, either the original exception or the one indicating the failure to close the stream. The finally block has no access to the pending exception however and is unaware of whether there is an exception pending or not. All it knows is an exception occurred during the execution of the finally block, and should throw that or wrap it in another exception - same handling as in Case 1.
try {
write();
flush();
finally {
try {
close();
catch (...) {
log();
}The flush() at the end of try seems kind of redundant, since close() calls flush() anyway. The benefit is that the try statement completion matches the try block ("real work") completion.
If we get to the end of the try block with no exception, then write() and flush() have succeeded and the data is where it needs to be. All that's left is to release the I/O resource, which will always be done in finally.
If there's an exception in the try block, it is propagated out, so we know of any failure that occurred doing the "real work." The I/O resource is still released in finally.
Regardless of how the try block completed, releasing the resource does not affect how the try statement completes, and hence does not supersede how our "real work" completes, which is all we care about. We still log any close() errors for later investigation. What matters to our program is whether all the data was written, and the completion of write() and flush() tells us that.

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4 Types of exception and the code to handle them

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