Compile Error for Unhandled Checked Exception

If you don't handle a checked exception, the code simply won't compile — and that's the key point, it's a compile-time failure, not something that blows up at runtime. The compiler enforces what's called the catch-or-declare rule. Whenever you call something that can throw a checked exception, like reading a file which throws I O exception, you have two choices. Either you catch it, by wrapping the call in a try-catch block and handling it there, or you declare it, by adding throws I O exception to your method's signature so that the responsibility passes up to whoever calls your method. If you do neither, the build fails with a message along the lines of unreported exception I O exception, must be caught or declared to be thrown. So you literally can't run the program until you deal with it one way or another. That compile-time enforcement is the entire practical meaning of the word checked — the compiler won't let you silently ignore it. Compare that to unchecked exceptions, the RuntimeException subclasses: code that might throw a NullPointerException compiles perfectly fine with no handling at all, because the compiler doesn't enforce anything for those. A couple of mistakes I'd warn against: don't just slap an empty catch block on it to make the compiler happy, because that swallows real failures silently. And don't reach for throws Exception to make it go away — declare the specific exception type instead, so the contract stays honest and callers know exactly what they're dealing with.