I am confused about types of exceptions in Java. On many tutorial websites I have seen that two types of exception are there in java Compile time exception Run time exception But when I talked wit... More on stackoverflow.com

I finally went on and wrote what i felt like i had to say in the context of exceptions. Since it's such a debated topic, i fully expect some negative backlash, and i have no problem with it, everybody is entitled to their opinion! Let me know if you find it somehow useful. More on reddit.com

The article has some errors. And not the throwable kind, heh: If not found, it unwinds the method-call stack looking for the closest catch block that can handle the exception. If not found, the JVM terminates with a suitable message. You can see this action in Listing 1. The part in italics is incorrect! What happens if there is no catch block that is suitable is that the thread exits and passes the exception that was never caught to the thread's uncaught exception handler. And that's that. The thread is done. By default, each thread starts with an uncaught exception handler that simply prints the exception to syserr (e.printStackTrace(); - that's the whole body, that's all). At no point does it ever exit a JVM. Of course, if you have a java app that never starts any threads, then the main thread is the only relevant thread, and if that exits due to an exception bubbling all the way up, yeah, sure, the JVM then exits as no non-daemon threads are running. But it feels ridiculous to handwave this away as 'oh we are just trying to keep it simple'. "The thread dies" is just as simple and much more accurate. You can invoke printStackTrace() directly, typically from a catch block. For example, consider a second version of the PrintStackTraceDemo application. This entire article keeps making pointless and misleading sidenotes. For example, it sidenotes 'you can also call printStackTrace(somePrintWriter) which is weird to mention; anybody can look at the API docs and discover this, and it's not like they're covering the entire API here. It's like I'm pointing out all the interesting aspects of the Mona Lisa and then casually remark: "Oh, look, someone dropped a candy wrapper over there. Anyway, moving right along..." - it's just bizarre to mention this. It strongly insinuates that this is important. And that then blows up thoroughly in the quoted section: Newbies are legendary in writing catch blocks with e.printStackTrace(); in it which is a massive anti-pattern that is difficult to eradicate. And this blog post is making it worse by using it as a way to explain that you can invoke printStackTrace yourself (not an important lesson!) without explaining that you shouldn't do that or that this contrived example shouldn't be taken as an insinuation of: "Ah, and this is how you write your standard catch block". Try-with-resources Another example that is fucking horrible. You don't deal with IOExceptions thrown by close() methods by ignoring them!! streams buffer. Any exception thrown by a close() method means the entire write operation has likely failed. If you treat them differently than any exception that would have been thrown by the most recent write call you wrote a hard-to-test for bug (i.e: A really really bad bug). But that isn't obvious here. It's again teaching extremely bad patterns. Listing 8. Copy.java No, the right way to deal with exceptions thrown here is to just declare your main method as throws Exception which you should almost always do. Writing a catch block that tosses most of the useful info in the garbage (as in this snippet, the exception's type which might be FileAccessDeniedException or whatnot - the key info, you toss that away!), then just writes something and blindly continues with the app is ON ERROR RESUME NEXT level stupidity. Common stupidity, but that shouldn't be an excuse. On the contrary, given that the common-ness has proven that your average new java programmer will readily misunderstand, you should go out of your way not to perpetuate this mistake. As is, this article should be torched with a flamethrower: If you send this to new java programmers and they read it, they'll be stupider after having read it than before. The article is fixable though. Come up with less 'actively perpetuating really stupid anti-patterns' examples, stop trying to be opinion-less (because the chosen examples and focus invoke an opinion, whether you intended it or not, and right now it's invoking the wrong ones), and cut some of the irrelevant chaff such as how to make your own stack trace (not relevant for an intro article in any way and actively misleads in suggesting that it is somehow an important tool one should be using often) and mentioning irrelevant parts of the API. More on reddit.com

What are you trying to do here? You have declared num to be an array, of length 10, containing Rational objects. That means that num[0], num[1], num[2], …, and num[9] are all individual Rational objects. The index to an array must be an integer: the 0th element of the array is num[0], the 3rd element is num[3], the 9th element is num[9], and so on. It doesn't make sense to use a Rational object as the index to an array. The expression num[u] doesn't make sense if u is a Rational object. What do you intend to mean by that?

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